xpc_sn2.c

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/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2008-2009 Silicon Graphics, Inc.  All Rights Reserved.
 */

/*
 * Cross Partition Communication (XPC) sn2-based functions.
 *
 *     Architecture specific implementation of common functions.
 *
 */

#include <linux/delay.h>
#include <linux/slab.h>
#include <asm/uncached.h>
#include <asm/sn/mspec.h>
#include <asm/sn/sn_sal.h>
#include "xpc.h"

/*
 * Define the number of u64s required to represent all the C-brick nasids
 * as a bitmap.  The cross-partition kernel modules deal only with
 * C-brick nasids, thus the need for bitmaps which don't account for
 * odd-numbered (non C-brick) nasids.
 */
#define XPC_MAX_PHYSNODES_SN2   (MAX_NUMALINK_NODES / 2)
#define XP_NASID_MASK_BYTES_SN2 ((XPC_MAX_PHYSNODES_SN2 + 7) / 8)
#define XP_NASID_MASK_WORDS_SN2 ((XPC_MAX_PHYSNODES_SN2 + 63) / 64)

/*
 * Memory for XPC's amo variables is allocated by the MSPEC driver. These
 * pages are located in the lowest granule. The lowest granule uses 4k pages
 * for cached references and an alternate TLB handler to never provide a
 * cacheable mapping for the entire region. This will prevent speculative
 * reading of cached copies of our lines from being issued which will cause
 * a PI FSB Protocol error to be generated by the SHUB. For XPC, we need 64
 * amo variables (based on XP_MAX_NPARTITIONS_SN2) to identify the senders of
 * NOTIFY IRQs, 128 amo variables (based on XP_NASID_MASK_WORDS_SN2) to identify
 * the senders of ACTIVATE IRQs, 1 amo variable to identify which remote
 * partitions (i.e., XPCs) consider themselves currently engaged with the
 * local XPC and 1 amo variable to request partition deactivation.
 */
#define XPC_NOTIFY_IRQ_AMOS_SN2     0
#define XPC_ACTIVATE_IRQ_AMOS_SN2   (XPC_NOTIFY_IRQ_AMOS_SN2 + \
                     XP_MAX_NPARTITIONS_SN2)
#define XPC_ENGAGED_PARTITIONS_AMO_SN2  (XPC_ACTIVATE_IRQ_AMOS_SN2 + \
                     XP_NASID_MASK_WORDS_SN2)
#define XPC_DEACTIVATE_REQUEST_AMO_SN2  (XPC_ENGAGED_PARTITIONS_AMO_SN2 + 1)

/*
 * Buffer used to store a local copy of portions of a remote partition's
 * reserved page (either its header and part_nasids mask, or its vars).
 */
static void *xpc_remote_copy_buffer_base_sn2;
static char *xpc_remote_copy_buffer_sn2;

static struct xpc_vars_sn2 *xpc_vars_sn2;
static struct xpc_vars_part_sn2 *xpc_vars_part_sn2;

static int
xpc_setup_partitions_sn2(void)
{
    /* nothing needs to be done */
    return 0;
}

static void
xpc_teardown_partitions_sn2(void)
{
    /* nothing needs to be done */
}

/* SH_IPI_ACCESS shub register value on startup */
static u64 xpc_sh1_IPI_access_sn2;
static u64 xpc_sh2_IPI_access0_sn2;
static u64 xpc_sh2_IPI_access1_sn2;
static u64 xpc_sh2_IPI_access2_sn2;
static u64 xpc_sh2_IPI_access3_sn2;

/*
 * Change protections to allow IPI operations.
 */
static void
xpc_allow_IPI_ops_sn2(void)
{
    int node;
    int nasid;

    /* !!! The following should get moved into SAL. */
    if (is_shub2()) {
        xpc_sh2_IPI_access0_sn2 =
            (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS0));
        xpc_sh2_IPI_access1_sn2 =
            (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS1));
        xpc_sh2_IPI_access2_sn2 =
            (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS2));
        xpc_sh2_IPI_access3_sn2 =
            (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH2_IPI_ACCESS3));

        for_each_online_node(node) {
            nasid = cnodeid_to_nasid(node);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                  -1UL);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                  -1UL);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                  -1UL);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                  -1UL);
        }
    } else {
        xpc_sh1_IPI_access_sn2 =
            (u64)HUB_L((u64 *)LOCAL_MMR_ADDR(SH1_IPI_ACCESS));

        for_each_online_node(node) {
            nasid = cnodeid_to_nasid(node);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                  -1UL);
        }
    }
}

/*
 * Restrict protections to disallow IPI operations.
 */
static void
xpc_disallow_IPI_ops_sn2(void)
{
    int node;
    int nasid;

    /* !!! The following should get moved into SAL. */
    if (is_shub2()) {
        for_each_online_node(node) {
            nasid = cnodeid_to_nasid(node);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS0),
                  xpc_sh2_IPI_access0_sn2);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS1),
                  xpc_sh2_IPI_access1_sn2);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS2),
                  xpc_sh2_IPI_access2_sn2);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH2_IPI_ACCESS3),
                  xpc_sh2_IPI_access3_sn2);
        }
    } else {
        for_each_online_node(node) {
            nasid = cnodeid_to_nasid(node);
            HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid, SH1_IPI_ACCESS),
                  xpc_sh1_IPI_access_sn2);
        }
    }
}

/*
 * The following set of functions are used for the sending and receiving of
 * IRQs (also known as IPIs). There are two flavors of IRQs, one that is
 * associated with partition activity (SGI_XPC_ACTIVATE) and the other that
 * is associated with channel activity (SGI_XPC_NOTIFY).
 */

static u64
xpc_receive_IRQ_amo_sn2(struct amo *amo)
{
    return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_CLEAR);
}

static enum xp_retval
xpc_send_IRQ_sn2(struct amo *amo, u64 flag, int nasid, int phys_cpuid,
         int vector)
{
    int ret = 0;
    unsigned long irq_flags;

    local_irq_save(irq_flags);

    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR, flag);
    sn_send_IPI_phys(nasid, phys_cpuid, vector, 0);

    /*
     * We must always use the nofault function regardless of whether we
     * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
     * didn't, we'd never know that the other partition is down and would
     * keep sending IRQs and amos to it until the heartbeat times out.
     */
    ret = xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->variable),
                             xp_nofault_PIOR_target));

    local_irq_restore(irq_flags);

    return (ret == 0) ? xpSuccess : xpPioReadError;
}

static struct amo *
xpc_init_IRQ_amo_sn2(int index)
{
    struct amo *amo = xpc_vars_sn2->amos_page + index;

    (void)xpc_receive_IRQ_amo_sn2(amo); /* clear amo variable */
    return amo;
}

/*
 * Functions associated with SGI_XPC_ACTIVATE IRQ.
 */

/*
 * Notify the heartbeat check thread that an activate IRQ has been received.
 */
static irqreturn_t
xpc_handle_activate_IRQ_sn2(int irq, void *dev_id)
{
    unsigned long irq_flags;

    spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
    xpc_activate_IRQ_rcvd++;
    spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

    wake_up_interruptible(&xpc_activate_IRQ_wq);
    return IRQ_HANDLED;
}

/*
 * Flag the appropriate amo variable and send an IRQ to the specified node.
 */
static void
xpc_send_activate_IRQ_sn2(unsigned long amos_page_pa, int from_nasid,
              int to_nasid, int to_phys_cpuid)
{
    struct amo *amos = (struct amo *)__va(amos_page_pa +
                          (XPC_ACTIVATE_IRQ_AMOS_SN2 *
                          sizeof(struct amo)));

    (void)xpc_send_IRQ_sn2(&amos[BIT_WORD(from_nasid / 2)],
                   BIT_MASK(from_nasid / 2), to_nasid,
                   to_phys_cpuid, SGI_XPC_ACTIVATE);
}

static void
xpc_send_local_activate_IRQ_sn2(int from_nasid)
{
    unsigned long irq_flags;
    struct amo *amos = (struct amo *)__va(xpc_vars_sn2->amos_page_pa +
                          (XPC_ACTIVATE_IRQ_AMOS_SN2 *
                          sizeof(struct amo)));

    /* fake the sending and receipt of an activate IRQ from remote nasid */
    FETCHOP_STORE_OP(TO_AMO((u64)&amos[BIT_WORD(from_nasid / 2)].variable),
             FETCHOP_OR, BIT_MASK(from_nasid / 2));

    spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
    xpc_activate_IRQ_rcvd++;
    spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

    wake_up_interruptible(&xpc_activate_IRQ_wq);
}

/*
 * Functions associated with SGI_XPC_NOTIFY IRQ.
 */

/*
 * Check to see if any chctl flags were sent from the specified partition.
 */
static void
xpc_check_for_sent_chctl_flags_sn2(struct xpc_partition *part)
{
    union xpc_channel_ctl_flags chctl;
    unsigned long irq_flags;

    chctl.all_flags = xpc_receive_IRQ_amo_sn2(part->sn.sn2.
                          local_chctl_amo_va);
    if (chctl.all_flags == 0)
        return;

    spin_lock_irqsave(&part->chctl_lock, irq_flags);
    part->chctl.all_flags |= chctl.all_flags;
    spin_unlock_irqrestore(&part->chctl_lock, irq_flags);

    dev_dbg(xpc_chan, "received notify IRQ from partid=%d, chctl.all_flags="
        "0x%llx\n", XPC_PARTID(part), chctl.all_flags);

    xpc_wakeup_channel_mgr(part);
}

/*
 * Handle the receipt of a SGI_XPC_NOTIFY IRQ by seeing whether the specified
 * partition actually sent it. Since SGI_XPC_NOTIFY IRQs may be shared by more
 * than one partition, we use an amo structure per partition to indicate
 * whether a partition has sent an IRQ or not.  If it has, then wake up the
 * associated kthread to handle it.
 *
 * All SGI_XPC_NOTIFY IRQs received by XPC are the result of IRQs sent by XPC
 * running on other partitions.
 *
 * Noteworthy Arguments:
 *
 *  irq - Interrupt ReQuest number. NOT USED.
 *
 *  dev_id - partid of IRQ's potential sender.
 */
static irqreturn_t
xpc_handle_notify_IRQ_sn2(int irq, void *dev_id)
{
    short partid = (short)(u64)dev_id;
    struct xpc_partition *part = &xpc_partitions[partid];

    DBUG_ON(partid < 0 || partid >= XP_MAX_NPARTITIONS_SN2);

    if (xpc_part_ref(part)) {
        xpc_check_for_sent_chctl_flags_sn2(part);

        xpc_part_deref(part);
    }
    return IRQ_HANDLED;
}

/*
 * Check to see if xpc_handle_notify_IRQ_sn2() dropped any IRQs on the floor
 * because the write to their associated amo variable completed after the IRQ
 * was received.
 */
static void
xpc_check_for_dropped_notify_IRQ_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

    if (xpc_part_ref(part)) {
        xpc_check_for_sent_chctl_flags_sn2(part);

        part_sn2->dropped_notify_IRQ_timer.expires = jiffies +
            XPC_DROPPED_NOTIFY_IRQ_WAIT_INTERVAL;
        add_timer(&part_sn2->dropped_notify_IRQ_timer);
        xpc_part_deref(part);
    }
}

/*
 * Send a notify IRQ to the remote partition that is associated with the
 * specified channel.
 */
static void
xpc_send_notify_IRQ_sn2(struct xpc_channel *ch, u8 chctl_flag,
            char *chctl_flag_string, unsigned long *irq_flags)
{
    struct xpc_partition *part = &xpc_partitions[ch->partid];
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    union xpc_channel_ctl_flags chctl = { 0 };
    enum xp_retval ret;

    if (likely(part->act_state != XPC_P_AS_DEACTIVATING)) {
        chctl.flags[ch->number] = chctl_flag;
        ret = xpc_send_IRQ_sn2(part_sn2->remote_chctl_amo_va,
                       chctl.all_flags,
                       part_sn2->notify_IRQ_nasid,
                       part_sn2->notify_IRQ_phys_cpuid,
                       SGI_XPC_NOTIFY);
        dev_dbg(xpc_chan, "%s sent to partid=%d, channel=%d, ret=%d\n",
            chctl_flag_string, ch->partid, ch->number, ret);
        if (unlikely(ret != xpSuccess)) {
            if (irq_flags != NULL)
                spin_unlock_irqrestore(&ch->lock, *irq_flags);
            XPC_DEACTIVATE_PARTITION(part, ret);
            if (irq_flags != NULL)
                spin_lock_irqsave(&ch->lock, *irq_flags);
        }
    }
}

#define XPC_SEND_NOTIFY_IRQ_SN2(_ch, _ipi_f, _irq_f) \
        xpc_send_notify_IRQ_sn2(_ch, _ipi_f, #_ipi_f, _irq_f)

/*
 * Make it look like the remote partition, which is associated with the
 * specified channel, sent us a notify IRQ. This faked IRQ will be handled
 * by xpc_check_for_dropped_notify_IRQ_sn2().
 */
static void
xpc_send_local_notify_IRQ_sn2(struct xpc_channel *ch, u8 chctl_flag,
                  char *chctl_flag_string)
{
    struct xpc_partition *part = &xpc_partitions[ch->partid];
    union xpc_channel_ctl_flags chctl = { 0 };

    chctl.flags[ch->number] = chctl_flag;
    FETCHOP_STORE_OP(TO_AMO((u64)&part->sn.sn2.local_chctl_amo_va->
                variable), FETCHOP_OR, chctl.all_flags);
    dev_dbg(xpc_chan, "%s sent local from partid=%d, channel=%d\n",
        chctl_flag_string, ch->partid, ch->number);
}

#define XPC_SEND_LOCAL_NOTIFY_IRQ_SN2(_ch, _ipi_f) \
        xpc_send_local_notify_IRQ_sn2(_ch, _ipi_f, #_ipi_f)

static void
xpc_send_chctl_closerequest_sn2(struct xpc_channel *ch,
                unsigned long *irq_flags)
{
    struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

    args->reason = ch->reason;
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_CLOSEREQUEST, irq_flags);
}

static void
xpc_send_chctl_closereply_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_CLOSEREPLY, irq_flags);
}

static void
xpc_send_chctl_openrequest_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
    struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

    args->entry_size = ch->entry_size;
    args->local_nentries = ch->local_nentries;
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_OPENREQUEST, irq_flags);
}

static void
xpc_send_chctl_openreply_sn2(struct xpc_channel *ch, unsigned long *irq_flags)
{
    struct xpc_openclose_args *args = ch->sn.sn2.local_openclose_args;

    args->remote_nentries = ch->remote_nentries;
    args->local_nentries = ch->local_nentries;
    args->local_msgqueue_pa = xp_pa(ch->sn.sn2.local_msgqueue);
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_OPENREPLY, irq_flags);
}

static void
xpc_send_chctl_opencomplete_sn2(struct xpc_channel *ch,
                unsigned long *irq_flags)
{
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_OPENCOMPLETE, irq_flags);
}

static void
xpc_send_chctl_msgrequest_sn2(struct xpc_channel *ch)
{
    XPC_SEND_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_MSGREQUEST, NULL);
}

static void
xpc_send_chctl_local_msgrequest_sn2(struct xpc_channel *ch)
{
    XPC_SEND_LOCAL_NOTIFY_IRQ_SN2(ch, XPC_CHCTL_MSGREQUEST);
}

static enum xp_retval
xpc_save_remote_msgqueue_pa_sn2(struct xpc_channel *ch,
                unsigned long msgqueue_pa)
{
    ch->sn.sn2.remote_msgqueue_pa = msgqueue_pa;
    return xpSuccess;
}

/*
 * This next set of functions are used to keep track of when a partition is
 * potentially engaged in accessing memory belonging to another partition.
 */

static void
xpc_indicate_partition_engaged_sn2(struct xpc_partition *part)
{
    unsigned long irq_flags;
    struct amo *amo = (struct amo *)__va(part->sn.sn2.remote_amos_page_pa +
                         (XPC_ENGAGED_PARTITIONS_AMO_SN2 *
                         sizeof(struct amo)));

    local_irq_save(irq_flags);

    /* set bit corresponding to our partid in remote partition's amo */
    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
             BIT(sn_partition_id));

    /*
     * We must always use the nofault function regardless of whether we
     * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
     * didn't, we'd never know that the other partition is down and would
     * keep sending IRQs and amos to it until the heartbeat times out.
     */
    (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                   variable),
                             xp_nofault_PIOR_target));

    local_irq_restore(irq_flags);
}

static void
xpc_indicate_partition_disengaged_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    unsigned long irq_flags;
    struct amo *amo = (struct amo *)__va(part_sn2->remote_amos_page_pa +
                         (XPC_ENGAGED_PARTITIONS_AMO_SN2 *
                         sizeof(struct amo)));

    local_irq_save(irq_flags);

    /* clear bit corresponding to our partid in remote partition's amo */
    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
             ~BIT(sn_partition_id));

    /*
     * We must always use the nofault function regardless of whether we
     * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
     * didn't, we'd never know that the other partition is down and would
     * keep sending IRQs and amos to it until the heartbeat times out.
     */
    (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                   variable),
                             xp_nofault_PIOR_target));

    local_irq_restore(irq_flags);

    /*
     * Send activate IRQ to get other side to see that we've cleared our
     * bit in their engaged partitions amo.
     */
    xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                  cnodeid_to_nasid(0),
                  part_sn2->activate_IRQ_nasid,
                  part_sn2->activate_IRQ_phys_cpuid);
}

static void
xpc_assume_partition_disengaged_sn2(short partid)
{
    struct amo *amo = xpc_vars_sn2->amos_page +
              XPC_ENGAGED_PARTITIONS_AMO_SN2;

    /* clear bit(s) based on partid mask in our partition's amo */
    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
             ~BIT(partid));
}

static int
xpc_partition_engaged_sn2(short partid)
{
    struct amo *amo = xpc_vars_sn2->amos_page +
              XPC_ENGAGED_PARTITIONS_AMO_SN2;

    /* our partition's amo variable ANDed with partid mask */
    return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
        BIT(partid)) != 0;
}

static int
xpc_any_partition_engaged_sn2(void)
{
    struct amo *amo = xpc_vars_sn2->amos_page +
              XPC_ENGAGED_PARTITIONS_AMO_SN2;

    /* our partition's amo variable */
    return FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) != 0;
}

/* original protection values for each node */
static u64 xpc_prot_vec_sn2[MAX_NUMNODES];

/*
 * Change protections to allow amo operations on non-Shub 1.1 systems.
 */
static enum xp_retval
xpc_allow_amo_ops_sn2(struct amo *amos_page)
{
    enum xp_retval ret = xpSuccess;

    /*
     * On SHUB 1.1, we cannot call sn_change_memprotect() since the BIST
     * collides with memory operations. On those systems we call
     * xpc_allow_amo_ops_shub_wars_1_1_sn2() instead.
     */
    if (!enable_shub_wars_1_1())
        ret = xp_expand_memprotect(ia64_tpa((u64)amos_page), PAGE_SIZE);

    return ret;
}

/*
 * Change protections to allow amo operations on Shub 1.1 systems.
 */
static void
xpc_allow_amo_ops_shub_wars_1_1_sn2(void)
{
    int node;
    int nasid;

    if (!enable_shub_wars_1_1())
        return;

    for_each_online_node(node) {
        nasid = cnodeid_to_nasid(node);
        /* save current protection values */
        xpc_prot_vec_sn2[node] =
            (u64)HUB_L((u64 *)GLOBAL_MMR_ADDR(nasid,
                          SH1_MD_DQLP_MMR_DIR_PRIVEC0));
        /* open up everything */
        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                         SH1_MD_DQLP_MMR_DIR_PRIVEC0),
              -1UL);
        HUB_S((u64 *)GLOBAL_MMR_ADDR(nasid,
                         SH1_MD_DQRP_MMR_DIR_PRIVEC0),
              -1UL);
    }
}

static enum xp_retval
xpc_get_partition_rsvd_page_pa_sn2(void *buf, u64 *cookie, unsigned long *rp_pa,
                   size_t *len)
{
    s64 status;
    enum xp_retval ret;

    status = sn_partition_reserved_page_pa((u64)buf, cookie,
            (u64 *)rp_pa, (u64 *)len);
    if (status == SALRET_OK)
        ret = xpSuccess;
    else if (status == SALRET_MORE_PASSES)
        ret = xpNeedMoreInfo;
    else
        ret = xpSalError;

    return ret;
}


static int
xpc_setup_rsvd_page_sn2(struct xpc_rsvd_page *rp)
{
    struct amo *amos_page;
    int i;
    int ret;

    xpc_vars_sn2 = XPC_RP_VARS(rp);

    rp->sn.sn2.vars_pa = xp_pa(xpc_vars_sn2);

    /* vars_part array follows immediately after vars */
    xpc_vars_part_sn2 = (struct xpc_vars_part_sn2 *)((u8 *)XPC_RP_VARS(rp) +
                             XPC_RP_VARS_SIZE);

    /*
     * Before clearing xpc_vars_sn2, see if a page of amos had been
     * previously allocated. If not we'll need to allocate one and set
     * permissions so that cross-partition amos are allowed.
     *
     * The allocated amo page needs MCA reporting to remain disabled after
     * XPC has unloaded.  To make this work, we keep a copy of the pointer
     * to this page (i.e., amos_page) in the struct xpc_vars_sn2 structure,
     * which is pointed to by the reserved page, and re-use that saved copy
     * on subsequent loads of XPC. This amo page is never freed, and its
     * memory protections are never restricted.
     */
    amos_page = xpc_vars_sn2->amos_page;
    if (amos_page == NULL) {
        amos_page = (struct amo *)TO_AMO(uncached_alloc_page(0, 1));
        if (amos_page == NULL) {
            dev_err(xpc_part, "can't allocate page of amos\n");
            return -ENOMEM;
        }

        /*
         * Open up amo-R/W to cpu.  This is done on Shub 1.1 systems
         * when xpc_allow_amo_ops_shub_wars_1_1_sn2() is called.
         */
        ret = xpc_allow_amo_ops_sn2(amos_page);
        if (ret != xpSuccess) {
            dev_err(xpc_part, "can't allow amo operations\n");
            uncached_free_page(__IA64_UNCACHED_OFFSET |
                       TO_PHYS((u64)amos_page), 1);
            return -EPERM;
        }
    }

    /* clear xpc_vars_sn2 */
    memset(xpc_vars_sn2, 0, sizeof(struct xpc_vars_sn2));

    xpc_vars_sn2->version = XPC_V_VERSION;
    xpc_vars_sn2->activate_IRQ_nasid = cpuid_to_nasid(0);
    xpc_vars_sn2->activate_IRQ_phys_cpuid = cpu_physical_id(0);
    xpc_vars_sn2->vars_part_pa = xp_pa(xpc_vars_part_sn2);
    xpc_vars_sn2->amos_page_pa = ia64_tpa((u64)amos_page);
    xpc_vars_sn2->amos_page = amos_page;    /* save for next load of XPC */

    /* clear xpc_vars_part_sn2 */
    memset((u64 *)xpc_vars_part_sn2, 0, sizeof(struct xpc_vars_part_sn2) *
           XP_MAX_NPARTITIONS_SN2);

    /* initialize the activate IRQ related amo variables */
    for (i = 0; i < xpc_nasid_mask_nlongs; i++)
        (void)xpc_init_IRQ_amo_sn2(XPC_ACTIVATE_IRQ_AMOS_SN2 + i);

    /* initialize the engaged remote partitions related amo variables */
    (void)xpc_init_IRQ_amo_sn2(XPC_ENGAGED_PARTITIONS_AMO_SN2);
    (void)xpc_init_IRQ_amo_sn2(XPC_DEACTIVATE_REQUEST_AMO_SN2);

    return 0;
}

static int
xpc_hb_allowed_sn2(short partid, void *heartbeating_to_mask)
{
    return test_bit(partid, heartbeating_to_mask);
}

static void
xpc_allow_hb_sn2(short partid)
{
    DBUG_ON(xpc_vars_sn2 == NULL);
    set_bit(partid, xpc_vars_sn2->heartbeating_to_mask);
}

static void
xpc_disallow_hb_sn2(short partid)
{
    DBUG_ON(xpc_vars_sn2 == NULL);
    clear_bit(partid, xpc_vars_sn2->heartbeating_to_mask);
}

static void
xpc_disallow_all_hbs_sn2(void)
{
    DBUG_ON(xpc_vars_sn2 == NULL);
    bitmap_zero(xpc_vars_sn2->heartbeating_to_mask, xp_max_npartitions);
}

static void
xpc_increment_heartbeat_sn2(void)
{
    xpc_vars_sn2->heartbeat++;
}

static void
xpc_offline_heartbeat_sn2(void)
{
    xpc_increment_heartbeat_sn2();
    xpc_vars_sn2->heartbeat_offline = 1;
}

static void
xpc_online_heartbeat_sn2(void)
{
    xpc_increment_heartbeat_sn2();
    xpc_vars_sn2->heartbeat_offline = 0;
}

static void
xpc_heartbeat_init_sn2(void)
{
    DBUG_ON(xpc_vars_sn2 == NULL);

    bitmap_zero(xpc_vars_sn2->heartbeating_to_mask, XP_MAX_NPARTITIONS_SN2);
    xpc_online_heartbeat_sn2();
}

static void
xpc_heartbeat_exit_sn2(void)
{
    xpc_offline_heartbeat_sn2();
}

static enum xp_retval
xpc_get_remote_heartbeat_sn2(struct xpc_partition *part)
{
    struct xpc_vars_sn2 *remote_vars;
    enum xp_retval ret;

    remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer_sn2;

    /* pull the remote vars structure that contains the heartbeat */
    ret = xp_remote_memcpy(xp_pa(remote_vars),
                   part->sn.sn2.remote_vars_pa,
                   XPC_RP_VARS_SIZE);
    if (ret != xpSuccess)
        return ret;

    dev_dbg(xpc_part, "partid=%d, heartbeat=%lld, last_heartbeat=%lld, "
        "heartbeat_offline=%lld, HB_mask[0]=0x%lx\n", XPC_PARTID(part),
        remote_vars->heartbeat, part->last_heartbeat,
        remote_vars->heartbeat_offline,
        remote_vars->heartbeating_to_mask[0]);

    if ((remote_vars->heartbeat == part->last_heartbeat &&
        !remote_vars->heartbeat_offline) ||
        !xpc_hb_allowed_sn2(sn_partition_id,
                remote_vars->heartbeating_to_mask)) {
        ret = xpNoHeartbeat;
    } else {
        part->last_heartbeat = remote_vars->heartbeat;
    }

    return ret;
}

/*
 * Get a copy of the remote partition's XPC variables from the reserved page.
 *
 * remote_vars points to a buffer that is cacheline aligned for BTE copies and
 * assumed to be of size XPC_RP_VARS_SIZE.
 */
static enum xp_retval
xpc_get_remote_vars_sn2(unsigned long remote_vars_pa,
            struct xpc_vars_sn2 *remote_vars)
{
    enum xp_retval ret;

    if (remote_vars_pa == 0)
        return xpVarsNotSet;

    /* pull over the cross partition variables */
    ret = xp_remote_memcpy(xp_pa(remote_vars), remote_vars_pa,
                   XPC_RP_VARS_SIZE);
    if (ret != xpSuccess)
        return ret;

    if (XPC_VERSION_MAJOR(remote_vars->version) !=
        XPC_VERSION_MAJOR(XPC_V_VERSION)) {
        return xpBadVersion;
    }

    return xpSuccess;
}

static void
xpc_request_partition_activation_sn2(struct xpc_rsvd_page *remote_rp,
                     unsigned long remote_rp_pa, int nasid)
{
    xpc_send_local_activate_IRQ_sn2(nasid);
}

static void
xpc_request_partition_reactivation_sn2(struct xpc_partition *part)
{
    xpc_send_local_activate_IRQ_sn2(part->sn.sn2.activate_IRQ_nasid);
}

static void
xpc_request_partition_deactivation_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    unsigned long irq_flags;
    struct amo *amo = (struct amo *)__va(part_sn2->remote_amos_page_pa +
                         (XPC_DEACTIVATE_REQUEST_AMO_SN2 *
                         sizeof(struct amo)));

    local_irq_save(irq_flags);

    /* set bit corresponding to our partid in remote partition's amo */
    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_OR,
             BIT(sn_partition_id));

    /*
     * We must always use the nofault function regardless of whether we
     * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
     * didn't, we'd never know that the other partition is down and would
     * keep sending IRQs and amos to it until the heartbeat times out.
     */
    (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                   variable),
                             xp_nofault_PIOR_target));

    local_irq_restore(irq_flags);

    /*
     * Send activate IRQ to get other side to see that we've set our
     * bit in their deactivate request amo.
     */
    xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                  cnodeid_to_nasid(0),
                  part_sn2->activate_IRQ_nasid,
                  part_sn2->activate_IRQ_phys_cpuid);
}

static void
xpc_cancel_partition_deactivation_request_sn2(struct xpc_partition *part)
{
    unsigned long irq_flags;
    struct amo *amo = (struct amo *)__va(part->sn.sn2.remote_amos_page_pa +
                         (XPC_DEACTIVATE_REQUEST_AMO_SN2 *
                         sizeof(struct amo)));

    local_irq_save(irq_flags);

    /* clear bit corresponding to our partid in remote partition's amo */
    FETCHOP_STORE_OP(TO_AMO((u64)&amo->variable), FETCHOP_AND,
             ~BIT(sn_partition_id));

    /*
     * We must always use the nofault function regardless of whether we
     * are on a Shub 1.1 system or a Shub 1.2 slice 0xc processor. If we
     * didn't, we'd never know that the other partition is down and would
     * keep sending IRQs and amos to it until the heartbeat times out.
     */
    (void)xp_nofault_PIOR((u64 *)GLOBAL_MMR_ADDR(NASID_GET(&amo->
                                   variable),
                             xp_nofault_PIOR_target));

    local_irq_restore(irq_flags);
}

static int
xpc_partition_deactivation_requested_sn2(short partid)
{
    struct amo *amo = xpc_vars_sn2->amos_page +
              XPC_DEACTIVATE_REQUEST_AMO_SN2;

    /* our partition's amo variable ANDed with partid mask */
    return (FETCHOP_LOAD_OP(TO_AMO((u64)&amo->variable), FETCHOP_LOAD) &
        BIT(partid)) != 0;
}

/*
 * Update the remote partition's info.
 */
static void
xpc_update_partition_info_sn2(struct xpc_partition *part, u8 remote_rp_version,
                  unsigned long *remote_rp_ts_jiffies,
                  unsigned long remote_rp_pa,
                  unsigned long remote_vars_pa,
                  struct xpc_vars_sn2 *remote_vars)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;

    part->remote_rp_version = remote_rp_version;
    dev_dbg(xpc_part, "  remote_rp_version = 0x%016x\n",
        part->remote_rp_version);

    part->remote_rp_ts_jiffies = *remote_rp_ts_jiffies;
    dev_dbg(xpc_part, "  remote_rp_ts_jiffies = 0x%016lx\n",
        part->remote_rp_ts_jiffies);

    part->remote_rp_pa = remote_rp_pa;
    dev_dbg(xpc_part, "  remote_rp_pa = 0x%016lx\n", part->remote_rp_pa);

    part_sn2->remote_vars_pa = remote_vars_pa;
    dev_dbg(xpc_part, "  remote_vars_pa = 0x%016lx\n",
        part_sn2->remote_vars_pa);

    part->last_heartbeat = remote_vars->heartbeat - 1;
    dev_dbg(xpc_part, "  last_heartbeat = 0x%016llx\n",
        part->last_heartbeat);

    part_sn2->remote_vars_part_pa = remote_vars->vars_part_pa;
    dev_dbg(xpc_part, "  remote_vars_part_pa = 0x%016lx\n",
        part_sn2->remote_vars_part_pa);

    part_sn2->activate_IRQ_nasid = remote_vars->activate_IRQ_nasid;
    dev_dbg(xpc_part, "  activate_IRQ_nasid = 0x%x\n",
        part_sn2->activate_IRQ_nasid);

    part_sn2->activate_IRQ_phys_cpuid =
        remote_vars->activate_IRQ_phys_cpuid;
    dev_dbg(xpc_part, "  activate_IRQ_phys_cpuid = 0x%x\n",
        part_sn2->activate_IRQ_phys_cpuid);

    part_sn2->remote_amos_page_pa = remote_vars->amos_page_pa;
    dev_dbg(xpc_part, "  remote_amos_page_pa = 0x%lx\n",
        part_sn2->remote_amos_page_pa);

    part_sn2->remote_vars_version = remote_vars->version;
    dev_dbg(xpc_part, "  remote_vars_version = 0x%x\n",
        part_sn2->remote_vars_version);
}

/*
 * Prior code has determined the nasid which generated a activate IRQ.
 * Inspect that nasid to determine if its partition needs to be activated
 * or deactivated.
 *
 * A partition is considered "awaiting activation" if our partition
 * flags indicate it is not active and it has a heartbeat.  A
 * partition is considered "awaiting deactivation" if our partition
 * flags indicate it is active but it has no heartbeat or it is not
 * sending its heartbeat to us.
 *
 * To determine the heartbeat, the remote nasid must have a properly
 * initialized reserved page.
 */
static void
xpc_identify_activate_IRQ_req_sn2(int nasid)
{
    struct xpc_rsvd_page *remote_rp;
    struct xpc_vars_sn2 *remote_vars;
    unsigned long remote_rp_pa;
    unsigned long remote_vars_pa;
    int remote_rp_version;
    int reactivate = 0;
    unsigned long remote_rp_ts_jiffies = 0;
    short partid;
    struct xpc_partition *part;
    struct xpc_partition_sn2 *part_sn2;
    enum xp_retval ret;

    /* pull over the reserved page structure */

    remote_rp = (struct xpc_rsvd_page *)xpc_remote_copy_buffer_sn2;

    ret = xpc_get_remote_rp(nasid, NULL, remote_rp, &remote_rp_pa);
    if (ret != xpSuccess) {
        dev_warn(xpc_part, "unable to get reserved page from nasid %d, "
             "which sent interrupt, reason=%d\n", nasid, ret);
        return;
    }

    remote_vars_pa = remote_rp->sn.sn2.vars_pa;
    remote_rp_version = remote_rp->version;
    remote_rp_ts_jiffies = remote_rp->ts_jiffies;

    partid = remote_rp->SAL_partid;
    part = &xpc_partitions[partid];
    part_sn2 = &part->sn.sn2;

    /* pull over the cross partition variables */

    remote_vars = (struct xpc_vars_sn2 *)xpc_remote_copy_buffer_sn2;

    ret = xpc_get_remote_vars_sn2(remote_vars_pa, remote_vars);
    if (ret != xpSuccess) {
        dev_warn(xpc_part, "unable to get XPC variables from nasid %d, "
             "which sent interrupt, reason=%d\n", nasid, ret);

        XPC_DEACTIVATE_PARTITION(part, ret);
        return;
    }

    part->activate_IRQ_rcvd++;

    dev_dbg(xpc_part, "partid for nasid %d is %d; IRQs = %d; HB = "
        "%lld:0x%lx\n", (int)nasid, (int)partid,
        part->activate_IRQ_rcvd,
        remote_vars->heartbeat, remote_vars->heartbeating_to_mask[0]);

    if (xpc_partition_disengaged(part) &&
        part->act_state == XPC_P_AS_INACTIVE) {

        xpc_update_partition_info_sn2(part, remote_rp_version,
                          &remote_rp_ts_jiffies,
                          remote_rp_pa, remote_vars_pa,
                          remote_vars);

        if (xpc_partition_deactivation_requested_sn2(partid)) {
            /*
             * Other side is waiting on us to deactivate even though
             * we already have.
             */
            return;
        }

        xpc_activate_partition(part);
        return;
    }

    DBUG_ON(part->remote_rp_version == 0);
    DBUG_ON(part_sn2->remote_vars_version == 0);

    if (remote_rp_ts_jiffies != part->remote_rp_ts_jiffies) {

        /* the other side rebooted */

        DBUG_ON(xpc_partition_engaged_sn2(partid));
        DBUG_ON(xpc_partition_deactivation_requested_sn2(partid));

        xpc_update_partition_info_sn2(part, remote_rp_version,
                          &remote_rp_ts_jiffies,
                          remote_rp_pa, remote_vars_pa,
                          remote_vars);
        reactivate = 1;
    }

    if (part->disengage_timeout > 0 && !xpc_partition_disengaged(part)) {
        /* still waiting on other side to disengage from us */
        return;
    }

    if (reactivate)
        XPC_DEACTIVATE_PARTITION(part, xpReactivating);
    else if (xpc_partition_deactivation_requested_sn2(partid))
        XPC_DEACTIVATE_PARTITION(part, xpOtherGoingDown);
}

/*
 * Loop through the activation amo variables and process any bits
 * which are set.  Each bit indicates a nasid sending a partition
 * activation or deactivation request.
 *
 * Return #of IRQs detected.
 */
int
xpc_identify_activate_IRQ_sender_sn2(void)
{
    int l;
    int b;
    unsigned long nasid_mask_long;
    u64 nasid;      /* remote nasid */
    int n_IRQs_detected = 0;
    struct amo *act_amos;

    act_amos = xpc_vars_sn2->amos_page + XPC_ACTIVATE_IRQ_AMOS_SN2;

    /* scan through activate amo variables looking for non-zero entries */
    for (l = 0; l < xpc_nasid_mask_nlongs; l++) {

        if (xpc_exiting)
            break;

        nasid_mask_long = xpc_receive_IRQ_amo_sn2(&act_amos[l]);

        b = find_first_bit(&nasid_mask_long, BITS_PER_LONG);
        if (b >= BITS_PER_LONG) {
            /* no IRQs from nasids in this amo variable */
            continue;
        }

        dev_dbg(xpc_part, "amo[%d] gave back 0x%lx\n", l,
            nasid_mask_long);

        /*
         * If this nasid has been added to the machine since
         * our partition was reset, this will retain the
         * remote nasid in our reserved pages machine mask.
         * This is used in the event of module reload.
         */
        xpc_mach_nasids[l] |= nasid_mask_long;

        /* locate the nasid(s) which sent interrupts */

        do {
            n_IRQs_detected++;
            nasid = (l * BITS_PER_LONG + b) * 2;
            dev_dbg(xpc_part, "interrupt from nasid %lld\n", nasid);
            xpc_identify_activate_IRQ_req_sn2(nasid);

            b = find_next_bit(&nasid_mask_long, BITS_PER_LONG,
                      b + 1);
        } while (b < BITS_PER_LONG);
    }
    return n_IRQs_detected;
}

static void
xpc_process_activate_IRQ_rcvd_sn2(void)
{
    unsigned long irq_flags;
    int n_IRQs_expected;
    int n_IRQs_detected;

    spin_lock_irqsave(&xpc_activate_IRQ_rcvd_lock, irq_flags);
    n_IRQs_expected = xpc_activate_IRQ_rcvd;
    xpc_activate_IRQ_rcvd = 0;
    spin_unlock_irqrestore(&xpc_activate_IRQ_rcvd_lock, irq_flags);

    n_IRQs_detected = xpc_identify_activate_IRQ_sender_sn2();
    if (n_IRQs_detected < n_IRQs_expected) {
        /* retry once to help avoid missing amo */
        (void)xpc_identify_activate_IRQ_sender_sn2();
    }
}

/*
 * Setup the channel structures that are sn2 specific.
 */
static enum xp_retval
xpc_setup_ch_structures_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    struct xpc_channel_sn2 *ch_sn2;
    enum xp_retval retval;
    int ret;
    int cpuid;
    int ch_number;
    struct timer_list *timer;
    short partid = XPC_PARTID(part);

    /* allocate all the required GET/PUT values */

    part_sn2->local_GPs =
        xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE, GFP_KERNEL,
                      &part_sn2->local_GPs_base);
    if (part_sn2->local_GPs == NULL) {
        dev_err(xpc_chan, "can't get memory for local get/put "
            "values\n");
        return xpNoMemory;
    }

    part_sn2->remote_GPs =
        xpc_kzalloc_cacheline_aligned(XPC_GP_SIZE, GFP_KERNEL,
                      &part_sn2->remote_GPs_base);
    if (part_sn2->remote_GPs == NULL) {
        dev_err(xpc_chan, "can't get memory for remote get/put "
            "values\n");
        retval = xpNoMemory;
        goto out_1;
    }

    part_sn2->remote_GPs_pa = 0;

    /* allocate all the required open and close args */

    part_sn2->local_openclose_args =
        xpc_kzalloc_cacheline_aligned(XPC_OPENCLOSE_ARGS_SIZE,
                      GFP_KERNEL, &part_sn2->
                      local_openclose_args_base);
    if (part_sn2->local_openclose_args == NULL) {
        dev_err(xpc_chan, "can't get memory for local connect args\n");
        retval = xpNoMemory;
        goto out_2;
    }

    part_sn2->remote_openclose_args_pa = 0;

    part_sn2->local_chctl_amo_va = xpc_init_IRQ_amo_sn2(partid);

    part_sn2->notify_IRQ_nasid = 0;
    part_sn2->notify_IRQ_phys_cpuid = 0;
    part_sn2->remote_chctl_amo_va = NULL;

    sprintf(part_sn2->notify_IRQ_owner, "xpc%02d", partid);
    ret = request_irq(SGI_XPC_NOTIFY, xpc_handle_notify_IRQ_sn2,
              IRQF_SHARED, part_sn2->notify_IRQ_owner,
              (void *)(u64)partid);
    if (ret != 0) {
        dev_err(xpc_chan, "can't register NOTIFY IRQ handler, "
            "errno=%d\n", -ret);
        retval = xpLackOfResources;
        goto out_3;
    }

    /* Setup a timer to check for dropped notify IRQs */
    timer = &part_sn2->dropped_notify_IRQ_timer;
    init_timer(timer);
    timer->function =
        (void (*)(unsigned long))xpc_check_for_dropped_notify_IRQ_sn2;
    timer->data = (unsigned long)part;
    timer->expires = jiffies + XPC_DROPPED_NOTIFY_IRQ_WAIT_INTERVAL;
    add_timer(timer);

    for (ch_number = 0; ch_number < part->nchannels; ch_number++) {
        ch_sn2 = &part->channels[ch_number].sn.sn2;

        ch_sn2->local_GP = &part_sn2->local_GPs[ch_number];
        ch_sn2->local_openclose_args =
            &part_sn2->local_openclose_args[ch_number];

        mutex_init(&ch_sn2->msg_to_pull_mutex);
    }

    /*
     * Setup the per partition specific variables required by the
     * remote partition to establish channel connections with us.
     *
     * The setting of the magic # indicates that these per partition
     * specific variables are ready to be used.
     */
    xpc_vars_part_sn2[partid].GPs_pa = xp_pa(part_sn2->local_GPs);
    xpc_vars_part_sn2[partid].openclose_args_pa =
        xp_pa(part_sn2->local_openclose_args);
    xpc_vars_part_sn2[partid].chctl_amo_pa =
        xp_pa(part_sn2->local_chctl_amo_va);
    cpuid = raw_smp_processor_id(); /* any CPU in this partition will do */
    xpc_vars_part_sn2[partid].notify_IRQ_nasid = cpuid_to_nasid(cpuid);
    xpc_vars_part_sn2[partid].notify_IRQ_phys_cpuid =
        cpu_physical_id(cpuid);
    xpc_vars_part_sn2[partid].nchannels = part->nchannels;
    xpc_vars_part_sn2[partid].magic = XPC_VP_MAGIC1_SN2;

    return xpSuccess;

    /* setup of ch structures failed */
out_3:
    kfree(part_sn2->local_openclose_args_base);
    part_sn2->local_openclose_args = NULL;
out_2:
    kfree(part_sn2->remote_GPs_base);
    part_sn2->remote_GPs = NULL;
out_1:
    kfree(part_sn2->local_GPs_base);
    part_sn2->local_GPs = NULL;
    return retval;
}

/*
 * Teardown the channel structures that are sn2 specific.
 */
static void
xpc_teardown_ch_structures_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    short partid = XPC_PARTID(part);

    /*
     * Indicate that the variables specific to the remote partition are no
     * longer available for its use.
     */
    xpc_vars_part_sn2[partid].magic = 0;

    /* in case we've still got outstanding timers registered... */
    del_timer_sync(&part_sn2->dropped_notify_IRQ_timer);
    free_irq(SGI_XPC_NOTIFY, (void *)(u64)partid);

    kfree(part_sn2->local_openclose_args_base);
    part_sn2->local_openclose_args = NULL;
    kfree(part_sn2->remote_GPs_base);
    part_sn2->remote_GPs = NULL;
    kfree(part_sn2->local_GPs_base);
    part_sn2->local_GPs = NULL;
    part_sn2->local_chctl_amo_va = NULL;
}

/*
 * Create a wrapper that hides the underlying mechanism for pulling a cacheline
 * (or multiple cachelines) from a remote partition.
 *
 * src_pa must be a cacheline aligned physical address on the remote partition.
 * dst must be a cacheline aligned virtual address on this partition.
 * cnt must be cacheline sized
 */
/* ??? Replace this function by call to xp_remote_memcpy() or bte_copy()? */
static enum xp_retval
xpc_pull_remote_cachelines_sn2(struct xpc_partition *part, void *dst,
                   const unsigned long src_pa, size_t cnt)
{
    enum xp_retval ret;

    DBUG_ON(src_pa != L1_CACHE_ALIGN(src_pa));
    DBUG_ON((unsigned long)dst != L1_CACHE_ALIGN((unsigned long)dst));
    DBUG_ON(cnt != L1_CACHE_ALIGN(cnt));

    if (part->act_state == XPC_P_AS_DEACTIVATING)
        return part->reason;

    ret = xp_remote_memcpy(xp_pa(dst), src_pa, cnt);
    if (ret != xpSuccess) {
        dev_dbg(xpc_chan, "xp_remote_memcpy() from partition %d failed,"
            " ret=%d\n", XPC_PARTID(part), ret);
    }
    return ret;
}

/*
 * Pull the remote per partition specific variables from the specified
 * partition.
 */
static enum xp_retval
xpc_pull_remote_vars_part_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    u8 buffer[L1_CACHE_BYTES * 2];
    struct xpc_vars_part_sn2 *pulled_entry_cacheline =
        (struct xpc_vars_part_sn2 *)L1_CACHE_ALIGN((u64)buffer);
    struct xpc_vars_part_sn2 *pulled_entry;
    unsigned long remote_entry_cacheline_pa;
    unsigned long remote_entry_pa;
    short partid = XPC_PARTID(part);
    enum xp_retval ret;

    /* pull the cacheline that contains the variables we're interested in */

    DBUG_ON(part_sn2->remote_vars_part_pa !=
        L1_CACHE_ALIGN(part_sn2->remote_vars_part_pa));
    DBUG_ON(sizeof(struct xpc_vars_part_sn2) != L1_CACHE_BYTES / 2);

    remote_entry_pa = part_sn2->remote_vars_part_pa +
        sn_partition_id * sizeof(struct xpc_vars_part_sn2);

    remote_entry_cacheline_pa = (remote_entry_pa & ~(L1_CACHE_BYTES - 1));

    pulled_entry = (struct xpc_vars_part_sn2 *)((u64)pulled_entry_cacheline
                            + (remote_entry_pa &
                            (L1_CACHE_BYTES - 1)));

    ret = xpc_pull_remote_cachelines_sn2(part, pulled_entry_cacheline,
                         remote_entry_cacheline_pa,
                         L1_CACHE_BYTES);
    if (ret != xpSuccess) {
        dev_dbg(xpc_chan, "failed to pull XPC vars_part from "
            "partition %d, ret=%d\n", partid, ret);
        return ret;
    }

    /* see if they've been set up yet */

    if (pulled_entry->magic != XPC_VP_MAGIC1_SN2 &&
        pulled_entry->magic != XPC_VP_MAGIC2_SN2) {

        if (pulled_entry->magic != 0) {
            dev_dbg(xpc_chan, "partition %d's XPC vars_part for "
                "partition %d has bad magic value (=0x%llx)\n",
                partid, sn_partition_id, pulled_entry->magic);
            return xpBadMagic;
        }

        /* they've not been initialized yet */
        return xpRetry;
    }

    if (xpc_vars_part_sn2[partid].magic == XPC_VP_MAGIC1_SN2) {

        /* validate the variables */

        if (pulled_entry->GPs_pa == 0 ||
            pulled_entry->openclose_args_pa == 0 ||
            pulled_entry->chctl_amo_pa == 0) {

            dev_err(xpc_chan, "partition %d's XPC vars_part for "
                "partition %d are not valid\n", partid,
                sn_partition_id);
            return xpInvalidAddress;
        }

        /* the variables we imported look to be valid */

        part_sn2->remote_GPs_pa = pulled_entry->GPs_pa;
        part_sn2->remote_openclose_args_pa =
            pulled_entry->openclose_args_pa;
        part_sn2->remote_chctl_amo_va =
            (struct amo *)__va(pulled_entry->chctl_amo_pa);
        part_sn2->notify_IRQ_nasid = pulled_entry->notify_IRQ_nasid;
        part_sn2->notify_IRQ_phys_cpuid =
            pulled_entry->notify_IRQ_phys_cpuid;

        if (part->nchannels > pulled_entry->nchannels)
            part->nchannels = pulled_entry->nchannels;

        /* let the other side know that we've pulled their variables */

        xpc_vars_part_sn2[partid].magic = XPC_VP_MAGIC2_SN2;
    }

    if (pulled_entry->magic == XPC_VP_MAGIC1_SN2)
        return xpRetry;

    return xpSuccess;
}

/*
 * Establish first contact with the remote partititon. This involves pulling
 * the XPC per partition variables from the remote partition and waiting for
 * the remote partition to pull ours.
 */
static enum xp_retval
xpc_make_first_contact_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    enum xp_retval ret;

    /*
     * Register the remote partition's amos with SAL so it can handle
     * and cleanup errors within that address range should the remote
     * partition go down. We don't unregister this range because it is
     * difficult to tell when outstanding writes to the remote partition
     * are finished and thus when it is safe to unregister. This should
     * not result in wasted space in the SAL xp_addr_region table because
     * we should get the same page for remote_amos_page_pa after module
     * reloads and system reboots.
     */
    if (sn_register_xp_addr_region(part_sn2->remote_amos_page_pa,
                       PAGE_SIZE, 1) < 0) {
        dev_warn(xpc_part, "xpc_activating(%d) failed to register "
             "xp_addr region\n", XPC_PARTID(part));

        ret = xpPhysAddrRegFailed;
        XPC_DEACTIVATE_PARTITION(part, ret);
        return ret;
    }

    /*
     * Send activate IRQ to get other side to activate if they've not
     * already begun to do so.
     */
    xpc_send_activate_IRQ_sn2(part_sn2->remote_amos_page_pa,
                  cnodeid_to_nasid(0),
                  part_sn2->activate_IRQ_nasid,
                  part_sn2->activate_IRQ_phys_cpuid);

    while ((ret = xpc_pull_remote_vars_part_sn2(part)) != xpSuccess) {
        if (ret != xpRetry) {
            XPC_DEACTIVATE_PARTITION(part, ret);
            return ret;
        }

        dev_dbg(xpc_part, "waiting to make first contact with "
            "partition %d\n", XPC_PARTID(part));

        /* wait a 1/4 of a second or so */
        (void)msleep_interruptible(250);

        if (part->act_state == XPC_P_AS_DEACTIVATING)
            return part->reason;
    }

    return xpSuccess;
}

/*
 * Get the chctl flags and pull the openclose args and/or remote GPs as needed.
 */
static u64
xpc_get_chctl_all_flags_sn2(struct xpc_partition *part)
{
    struct xpc_partition_sn2 *part_sn2 = &part->sn.sn2;
    unsigned long irq_flags;
    union xpc_channel_ctl_flags chctl;
    enum xp_retval ret;

    /*
     * See if there are any chctl flags to be handled.
     */

    spin_lock_irqsave(&part->chctl_lock, irq_flags);
    chctl = part->chctl;
    if (chctl.all_flags != 0)
        part->chctl.all_flags = 0;

    spin_unlock_irqrestore(&part->chctl_lock, irq_flags);

    if (xpc_any_openclose_chctl_flags_set(&chctl)) {
        ret = xpc_pull_remote_cachelines_sn2(part, part->
                             remote_openclose_args,
                             part_sn2->
                             remote_openclose_args_pa,
                             XPC_OPENCLOSE_ARGS_SIZE);
        if (ret != xpSuccess) {
            XPC_DEACTIVATE_PARTITION(part, ret);

            dev_dbg(xpc_chan, "failed to pull openclose args from "
                "partition %d, ret=%d\n", XPC_PARTID(part),
                ret);

            /* don't bother processing chctl flags anymore */
            chctl.all_flags = 0;
        }
    }

    if (xpc_any_msg_chctl_flags_set(&chctl)) {
        ret = xpc_pull_remote_cachelines_sn2(part, part_sn2->remote_GPs,
                             part_sn2->remote_GPs_pa,
                             XPC_GP_SIZE);
        if (ret != xpSuccess) {
            XPC_DEACTIVATE_PARTITION(part, ret);

            dev_dbg(xpc_chan, "failed to pull GPs from partition "
                "%d, ret=%d\n", XPC_PARTID(part), ret);

            /* don't bother processing chctl flags anymore */
            chctl.all_flags = 0;
        }
    }

    return chctl.all_flags;
}

/*
 * Allocate the local message queue and the notify queue.
 */
static enum xp_retval
xpc_allocate_local_msgqueue_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    unsigned long irq_flags;
    int nentries;
    size_t nbytes;

    for (nentries = ch->local_nentries; nentries > 0; nentries--) {

        nbytes = nentries * ch->entry_size;
        ch_sn2->local_msgqueue =
            xpc_kzalloc_cacheline_aligned(nbytes, GFP_KERNEL,
                          &ch_sn2->local_msgqueue_base);
        if (ch_sn2->local_msgqueue == NULL)
            continue;

        nbytes = nentries * sizeof(struct xpc_notify_sn2);
        ch_sn2->notify_queue = kzalloc(nbytes, GFP_KERNEL);
        if (ch_sn2->notify_queue == NULL) {
            kfree(ch_sn2->local_msgqueue_base);
            ch_sn2->local_msgqueue = NULL;
            continue;
        }

        spin_lock_irqsave(&ch->lock, irq_flags);
        if (nentries < ch->local_nentries) {
            dev_dbg(xpc_chan, "nentries=%d local_nentries=%d, "
                "partid=%d, channel=%d\n", nentries,
                ch->local_nentries, ch->partid, ch->number);

            ch->local_nentries = nentries;
        }
        spin_unlock_irqrestore(&ch->lock, irq_flags);
        return xpSuccess;
    }

    dev_dbg(xpc_chan, "can't get memory for local message queue and notify "
        "queue, partid=%d, channel=%d\n", ch->partid, ch->number);
    return xpNoMemory;
}

/*
 * Allocate the cached remote message queue.
 */
static enum xp_retval
xpc_allocate_remote_msgqueue_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    unsigned long irq_flags;
    int nentries;
    size_t nbytes;

    DBUG_ON(ch->remote_nentries <= 0);

    for (nentries = ch->remote_nentries; nentries > 0; nentries--) {

        nbytes = nentries * ch->entry_size;
        ch_sn2->remote_msgqueue =
            xpc_kzalloc_cacheline_aligned(nbytes, GFP_KERNEL, &ch_sn2->
                          remote_msgqueue_base);
        if (ch_sn2->remote_msgqueue == NULL)
            continue;

        spin_lock_irqsave(&ch->lock, irq_flags);
        if (nentries < ch->remote_nentries) {
            dev_dbg(xpc_chan, "nentries=%d remote_nentries=%d, "
                "partid=%d, channel=%d\n", nentries,
                ch->remote_nentries, ch->partid, ch->number);

            ch->remote_nentries = nentries;
        }
        spin_unlock_irqrestore(&ch->lock, irq_flags);
        return xpSuccess;
    }

    dev_dbg(xpc_chan, "can't get memory for cached remote message queue, "
        "partid=%d, channel=%d\n", ch->partid, ch->number);
    return xpNoMemory;
}

/*
 * Allocate message queues and other stuff associated with a channel.
 *
 * Note: Assumes all of the channel sizes are filled in.
 */
static enum xp_retval
xpc_setup_msg_structures_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    enum xp_retval ret;

    DBUG_ON(ch->flags & XPC_C_SETUP);

    ret = xpc_allocate_local_msgqueue_sn2(ch);
    if (ret == xpSuccess) {

        ret = xpc_allocate_remote_msgqueue_sn2(ch);
        if (ret != xpSuccess) {
            kfree(ch_sn2->local_msgqueue_base);
            ch_sn2->local_msgqueue = NULL;
            kfree(ch_sn2->notify_queue);
            ch_sn2->notify_queue = NULL;
        }
    }
    return ret;
}

/*
 * Free up message queues and other stuff that were allocated for the specified
 * channel.
 */
static void
xpc_teardown_msg_structures_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;

    DBUG_ON(!spin_is_locked(&ch->lock));

    ch_sn2->remote_msgqueue_pa = 0;

    ch_sn2->local_GP->get = 0;
    ch_sn2->local_GP->put = 0;
    ch_sn2->remote_GP.get = 0;
    ch_sn2->remote_GP.put = 0;
    ch_sn2->w_local_GP.get = 0;
    ch_sn2->w_local_GP.put = 0;
    ch_sn2->w_remote_GP.get = 0;
    ch_sn2->w_remote_GP.put = 0;
    ch_sn2->next_msg_to_pull = 0;

    if (ch->flags & XPC_C_SETUP) {
        dev_dbg(xpc_chan, "ch->flags=0x%x, partid=%d, channel=%d\n",
            ch->flags, ch->partid, ch->number);

        kfree(ch_sn2->local_msgqueue_base);
        ch_sn2->local_msgqueue = NULL;
        kfree(ch_sn2->remote_msgqueue_base);
        ch_sn2->remote_msgqueue = NULL;
        kfree(ch_sn2->notify_queue);
        ch_sn2->notify_queue = NULL;
    }
}

/*
 * Notify those who wanted to be notified upon delivery of their message.
 */
static void
xpc_notify_senders_sn2(struct xpc_channel *ch, enum xp_retval reason, s64 put)
{
    struct xpc_notify_sn2 *notify;
    u8 notify_type;
    s64 get = ch->sn.sn2.w_remote_GP.get - 1;

    while (++get < put && atomic_read(&ch->n_to_notify) > 0) {

        notify = &ch->sn.sn2.notify_queue[get % ch->local_nentries];

        /*
         * See if the notify entry indicates it was associated with
         * a message who's sender wants to be notified. It is possible
         * that it is, but someone else is doing or has done the
         * notification.
         */
        notify_type = notify->type;
        if (notify_type == 0 ||
            cmpxchg(&notify->type, notify_type, 0) != notify_type) {
            continue;
        }

        DBUG_ON(notify_type != XPC_N_CALL);

        atomic_dec(&ch->n_to_notify);

        if (notify->func != NULL) {
            dev_dbg(xpc_chan, "notify->func() called, notify=0x%p "
                "msg_number=%lld partid=%d channel=%d\n",
                (void *)notify, get, ch->partid, ch->number);

            notify->func(reason, ch->partid, ch->number,
                     notify->key);

            dev_dbg(xpc_chan, "notify->func() returned, notify=0x%p"
                " msg_number=%lld partid=%d channel=%d\n",
                (void *)notify, get, ch->partid, ch->number);
        }
    }
}

static void
xpc_notify_senders_of_disconnect_sn2(struct xpc_channel *ch)
{
    xpc_notify_senders_sn2(ch, ch->reason, ch->sn.sn2.w_local_GP.put);
}

/*
 * Clear some of the msg flags in the local message queue.
 */
static inline void
xpc_clear_local_msgqueue_flags_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    s64 get;

    get = ch_sn2->w_remote_GP.get;
    do {
        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->local_msgqueue +
                         (get % ch->local_nentries) *
                         ch->entry_size);
        DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
        msg->flags = 0;
    } while (++get < ch_sn2->remote_GP.get);
}

/*
 * Clear some of the msg flags in the remote message queue.
 */
static inline void
xpc_clear_remote_msgqueue_flags_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    s64 put, remote_nentries = ch->remote_nentries;

    /* flags are zeroed when the buffer is allocated */
    if (ch_sn2->remote_GP.put < remote_nentries)
        return;

    put = max(ch_sn2->w_remote_GP.put, remote_nentries);
    do {
        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue +
                         (put % remote_nentries) *
                         ch->entry_size);
        DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
        DBUG_ON(!(msg->flags & XPC_M_SN2_DONE));
        DBUG_ON(msg->number != put - remote_nentries);
        msg->flags = 0;
    } while (++put < ch_sn2->remote_GP.put);
}

static int
xpc_n_of_deliverable_payloads_sn2(struct xpc_channel *ch)
{
    return ch->sn.sn2.w_remote_GP.put - ch->sn.sn2.w_local_GP.get;
}

static void
xpc_process_msg_chctl_flags_sn2(struct xpc_partition *part, int ch_number)
{
    struct xpc_channel *ch = &part->channels[ch_number];
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    int npayloads_sent;

    ch_sn2->remote_GP = part->sn.sn2.remote_GPs[ch_number];

    /* See what, if anything, has changed for each connected channel */

    xpc_msgqueue_ref(ch);

    if (ch_sn2->w_remote_GP.get == ch_sn2->remote_GP.get &&
        ch_sn2->w_remote_GP.put == ch_sn2->remote_GP.put) {
        /* nothing changed since GPs were last pulled */
        xpc_msgqueue_deref(ch);
        return;
    }

    if (!(ch->flags & XPC_C_CONNECTED)) {
        xpc_msgqueue_deref(ch);
        return;
    }

    /*
     * First check to see if messages recently sent by us have been
     * received by the other side. (The remote GET value will have
     * changed since we last looked at it.)
     */

    if (ch_sn2->w_remote_GP.get != ch_sn2->remote_GP.get) {

        /*
         * We need to notify any senders that want to be notified
         * that their sent messages have been received by their
         * intended recipients. We need to do this before updating
         * w_remote_GP.get so that we don't allocate the same message
         * queue entries prematurely (see xpc_allocate_msg()).
         */
        if (atomic_read(&ch->n_to_notify) > 0) {
            /*
             * Notify senders that messages sent have been
             * received and delivered by the other side.
             */
            xpc_notify_senders_sn2(ch, xpMsgDelivered,
                           ch_sn2->remote_GP.get);
        }

        /*
         * Clear msg->flags in previously sent messages, so that
         * they're ready for xpc_allocate_msg().
         */
        xpc_clear_local_msgqueue_flags_sn2(ch);

        ch_sn2->w_remote_GP.get = ch_sn2->remote_GP.get;

        dev_dbg(xpc_chan, "w_remote_GP.get changed to %lld, partid=%d, "
            "channel=%d\n", ch_sn2->w_remote_GP.get, ch->partid,
            ch->number);

        /*
         * If anyone was waiting for message queue entries to become
         * available, wake them up.
         */
        if (atomic_read(&ch->n_on_msg_allocate_wq) > 0)
            wake_up(&ch->msg_allocate_wq);
    }

    /*
     * Now check for newly sent messages by the other side. (The remote
     * PUT value will have changed since we last looked at it.)
     */

    if (ch_sn2->w_remote_GP.put != ch_sn2->remote_GP.put) {
        /*
         * Clear msg->flags in previously received messages, so that
         * they're ready for xpc_get_deliverable_payload_sn2().
         */
        xpc_clear_remote_msgqueue_flags_sn2(ch);

        smp_wmb(); /* ensure flags have been cleared before bte_copy */
        ch_sn2->w_remote_GP.put = ch_sn2->remote_GP.put;

        dev_dbg(xpc_chan, "w_remote_GP.put changed to %lld, partid=%d, "
            "channel=%d\n", ch_sn2->w_remote_GP.put, ch->partid,
            ch->number);

        npayloads_sent = xpc_n_of_deliverable_payloads_sn2(ch);
        if (npayloads_sent > 0) {
            dev_dbg(xpc_chan, "msgs waiting to be copied and "
                "delivered=%d, partid=%d, channel=%d\n",
                npayloads_sent, ch->partid, ch->number);

            if (ch->flags & XPC_C_CONNECTEDCALLOUT_MADE)
                xpc_activate_kthreads(ch, npayloads_sent);
        }
    }

    xpc_msgqueue_deref(ch);
}

static struct xpc_msg_sn2 *
xpc_pull_remote_msg_sn2(struct xpc_channel *ch, s64 get)
{
    struct xpc_partition *part = &xpc_partitions[ch->partid];
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    unsigned long remote_msg_pa;
    struct xpc_msg_sn2 *msg;
    u32 msg_index;
    u32 nmsgs;
    u64 msg_offset;
    enum xp_retval ret;

    if (mutex_lock_interruptible(&ch_sn2->msg_to_pull_mutex) != 0) {
        /* we were interrupted by a signal */
        return NULL;
    }

    while (get >= ch_sn2->next_msg_to_pull) {

        /* pull as many messages as are ready and able to be pulled */

        msg_index = ch_sn2->next_msg_to_pull % ch->remote_nentries;

        DBUG_ON(ch_sn2->next_msg_to_pull >= ch_sn2->w_remote_GP.put);
        nmsgs = ch_sn2->w_remote_GP.put - ch_sn2->next_msg_to_pull;
        if (msg_index + nmsgs > ch->remote_nentries) {
            /* ignore the ones that wrap the msg queue for now */
            nmsgs = ch->remote_nentries - msg_index;
        }

        msg_offset = msg_index * ch->entry_size;
        msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue +
            msg_offset);
        remote_msg_pa = ch_sn2->remote_msgqueue_pa + msg_offset;

        ret = xpc_pull_remote_cachelines_sn2(part, msg, remote_msg_pa,
                             nmsgs * ch->entry_size);
        if (ret != xpSuccess) {

            dev_dbg(xpc_chan, "failed to pull %d msgs starting with"
                " msg %lld from partition %d, channel=%d, "
                "ret=%d\n", nmsgs, ch_sn2->next_msg_to_pull,
                ch->partid, ch->number, ret);

            XPC_DEACTIVATE_PARTITION(part, ret);

            mutex_unlock(&ch_sn2->msg_to_pull_mutex);
            return NULL;
        }

        ch_sn2->next_msg_to_pull += nmsgs;
    }

    mutex_unlock(&ch_sn2->msg_to_pull_mutex);

    /* return the message we were looking for */
    msg_offset = (get % ch->remote_nentries) * ch->entry_size;
    msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->remote_msgqueue + msg_offset);

    return msg;
}

/*
 * Get the next deliverable message's payload.
 */
static void *
xpc_get_deliverable_payload_sn2(struct xpc_channel *ch)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    void *payload = NULL;
    s64 get;

    do {
        if (ch->flags & XPC_C_DISCONNECTING)
            break;

        get = ch_sn2->w_local_GP.get;
        smp_rmb();  /* guarantee that .get loads before .put */
        if (get == ch_sn2->w_remote_GP.put)
            break;

        /* There are messages waiting to be pulled and delivered.
         * We need to try to secure one for ourselves. We'll do this
         * by trying to increment w_local_GP.get and hope that no one
         * else beats us to it. If they do, we'll we'll simply have
         * to try again for the next one.
         */

        if (cmpxchg(&ch_sn2->w_local_GP.get, get, get + 1) == get) {
            /* we got the entry referenced by get */

            dev_dbg(xpc_chan, "w_local_GP.get changed to %lld, "
                "partid=%d, channel=%d\n", get + 1,
                ch->partid, ch->number);

            /* pull the message from the remote partition */

            msg = xpc_pull_remote_msg_sn2(ch, get);

            if (msg != NULL) {
                DBUG_ON(msg->number != get);
                DBUG_ON(msg->flags & XPC_M_SN2_DONE);
                DBUG_ON(!(msg->flags & XPC_M_SN2_READY));

                payload = &msg->payload;
            }
            break;
        }

    } while (1);

    return payload;
}

/*
 * Now we actually send the messages that are ready to be sent by advancing
 * the local message queue's Put value and then send a chctl msgrequest to the
 * recipient partition.
 */
static void
xpc_send_msgs_sn2(struct xpc_channel *ch, s64 initial_put)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    s64 put = initial_put + 1;
    int send_msgrequest = 0;

    while (1) {

        while (1) {
            if (put == ch_sn2->w_local_GP.put)
                break;

            msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->
                             local_msgqueue + (put %
                             ch->local_nentries) *
                             ch->entry_size);

            if (!(msg->flags & XPC_M_SN2_READY))
                break;

            put++;
        }

        if (put == initial_put) {
            /* nothing's changed */
            break;
        }

        if (cmpxchg_rel(&ch_sn2->local_GP->put, initial_put, put) !=
            initial_put) {
            /* someone else beat us to it */
            DBUG_ON(ch_sn2->local_GP->put < initial_put);
            break;
        }

        /* we just set the new value of local_GP->put */

        dev_dbg(xpc_chan, "local_GP->put changed to %lld, partid=%d, "
            "channel=%d\n", put, ch->partid, ch->number);

        send_msgrequest = 1;

        /*
         * We need to ensure that the message referenced by
         * local_GP->put is not XPC_M_SN2_READY or that local_GP->put
         * equals w_local_GP.put, so we'll go have a look.
         */
        initial_put = put;
    }

    if (send_msgrequest)
        xpc_send_chctl_msgrequest_sn2(ch);
}

/*
 * Allocate an entry for a message from the message queue associated with the
 * specified channel.
 */
static enum xp_retval
xpc_allocate_msg_sn2(struct xpc_channel *ch, u32 flags,
             struct xpc_msg_sn2 **address_of_msg)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    enum xp_retval ret;
    s64 put;

    /*
     * Get the next available message entry from the local message queue.
     * If none are available, we'll make sure that we grab the latest
     * GP values.
     */
    ret = xpTimeout;

    while (1) {

        put = ch_sn2->w_local_GP.put;
        smp_rmb();  /* guarantee that .put loads before .get */
        if (put - ch_sn2->w_remote_GP.get < ch->local_nentries) {

            /* There are available message entries. We need to try
             * to secure one for ourselves. We'll do this by trying
             * to increment w_local_GP.put as long as someone else
             * doesn't beat us to it. If they do, we'll have to
             * try again.
             */
            if (cmpxchg(&ch_sn2->w_local_GP.put, put, put + 1) ==
                put) {
                /* we got the entry referenced by put */
                break;
            }
            continue;   /* try again */
        }

        /*
         * There aren't any available msg entries at this time.
         *
         * In waiting for a message entry to become available,
         * we set a timeout in case the other side is not sending
         * completion interrupts. This lets us fake a notify IRQ
         * that will cause the notify IRQ handler to fetch the latest
         * GP values as if an interrupt was sent by the other side.
         */
        if (ret == xpTimeout)
            xpc_send_chctl_local_msgrequest_sn2(ch);

        if (flags & XPC_NOWAIT)
            return xpNoWait;

        ret = xpc_allocate_msg_wait(ch);
        if (ret != xpInterrupted && ret != xpTimeout)
            return ret;
    }

    /* get the message's address and initialize it */
    msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->local_msgqueue +
                     (put % ch->local_nentries) *
                     ch->entry_size);

    DBUG_ON(msg->flags != 0);
    msg->number = put;

    dev_dbg(xpc_chan, "w_local_GP.put changed to %lld; msg=0x%p, "
        "msg_number=%lld, partid=%d, channel=%d\n", put + 1,
        (void *)msg, msg->number, ch->partid, ch->number);

    *address_of_msg = msg;
    return xpSuccess;
}

/*
 * Common code that does the actual sending of the message by advancing the
 * local message queue's Put value and sends a chctl msgrequest to the
 * partition the message is being sent to.
 */
static enum xp_retval
xpc_send_payload_sn2(struct xpc_channel *ch, u32 flags, void *payload,
             u16 payload_size, u8 notify_type, xpc_notify_func func,
             void *key)
{
    enum xp_retval ret = xpSuccess;
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg = msg;
    struct xpc_notify_sn2 *notify = notify;
    s64 msg_number;
    s64 put;

    DBUG_ON(notify_type == XPC_N_CALL && func == NULL);

    if (XPC_MSG_SIZE(payload_size) > ch->entry_size)
        return xpPayloadTooBig;

    xpc_msgqueue_ref(ch);

    if (ch->flags & XPC_C_DISCONNECTING) {
        ret = ch->reason;
        goto out_1;
    }
    if (!(ch->flags & XPC_C_CONNECTED)) {
        ret = xpNotConnected;
        goto out_1;
    }

    ret = xpc_allocate_msg_sn2(ch, flags, &msg);
    if (ret != xpSuccess)
        goto out_1;

    msg_number = msg->number;

    if (notify_type != 0) {
        /*
         * Tell the remote side to send an ACK interrupt when the
         * message has been delivered.
         */
        msg->flags |= XPC_M_SN2_INTERRUPT;

        atomic_inc(&ch->n_to_notify);

        notify = &ch_sn2->notify_queue[msg_number % ch->local_nentries];
        notify->func = func;
        notify->key = key;
        notify->type = notify_type;

        /* ??? Is a mb() needed here? */

        if (ch->flags & XPC_C_DISCONNECTING) {
            /*
             * An error occurred between our last error check and
             * this one. We will try to clear the type field from
             * the notify entry. If we succeed then
             * xpc_disconnect_channel() didn't already process
             * the notify entry.
             */
            if (cmpxchg(&notify->type, notify_type, 0) ==
                notify_type) {
                atomic_dec(&ch->n_to_notify);
                ret = ch->reason;
            }
            goto out_1;
        }
    }

    memcpy(&msg->payload, payload, payload_size);

    msg->flags |= XPC_M_SN2_READY;

    /*
     * The preceding store of msg->flags must occur before the following
     * load of local_GP->put.
     */
    smp_mb();

    /* see if the message is next in line to be sent, if so send it */

    put = ch_sn2->local_GP->put;
    if (put == msg_number)
        xpc_send_msgs_sn2(ch, put);

out_1:
    xpc_msgqueue_deref(ch);
    return ret;
}

/*
 * Now we actually acknowledge the messages that have been delivered and ack'd
 * by advancing the cached remote message queue's Get value and if requested
 * send a chctl msgrequest to the message sender's partition.
 *
 * If a message has XPC_M_SN2_INTERRUPT set, send an interrupt to the partition
 * that sent the message.
 */
static void
xpc_acknowledge_msgs_sn2(struct xpc_channel *ch, s64 initial_get, u8 msg_flags)
{
    struct xpc_channel_sn2 *ch_sn2 = &ch->sn.sn2;
    struct xpc_msg_sn2 *msg;
    s64 get = initial_get + 1;
    int send_msgrequest = 0;

    while (1) {

        while (1) {
            if (get == ch_sn2->w_local_GP.get)
                break;

            msg = (struct xpc_msg_sn2 *)((u64)ch_sn2->
                             remote_msgqueue + (get %
                             ch->remote_nentries) *
                             ch->entry_size);

            if (!(msg->flags & XPC_M_SN2_DONE))
                break;

            msg_flags |= msg->flags;
            get++;
        }

        if (get == initial_get) {
            /* nothing's changed */
            break;
        }

        if (cmpxchg_rel(&ch_sn2->local_GP->get, initial_get, get) !=
            initial_get) {
            /* someone else beat us to it */
            DBUG_ON(ch_sn2->local_GP->get <= initial_get);
            break;
        }

        /* we just set the new value of local_GP->get */

        dev_dbg(xpc_chan, "local_GP->get changed to %lld, partid=%d, "
            "channel=%d\n", get, ch->partid, ch->number);

        send_msgrequest = (msg_flags & XPC_M_SN2_INTERRUPT);

        /*
         * We need to ensure that the message referenced by
         * local_GP->get is not XPC_M_SN2_DONE or that local_GP->get
         * equals w_local_GP.get, so we'll go have a look.
         */
        initial_get = get;
    }

    if (send_msgrequest)
        xpc_send_chctl_msgrequest_sn2(ch);
}

static void
xpc_received_payload_sn2(struct xpc_channel *ch, void *payload)
{
    struct xpc_msg_sn2 *msg;
    s64 msg_number;
    s64 get;

    msg = container_of(payload, struct xpc_msg_sn2, payload);
    msg_number = msg->number;

    dev_dbg(xpc_chan, "msg=0x%p, msg_number=%lld, partid=%d, channel=%d\n",
        (void *)msg, msg_number, ch->partid, ch->number);

    DBUG_ON((((u64)msg - (u64)ch->sn.sn2.remote_msgqueue) / ch->entry_size) !=
        msg_number % ch->remote_nentries);
    DBUG_ON(!(msg->flags & XPC_M_SN2_READY));
    DBUG_ON(msg->flags & XPC_M_SN2_DONE);

    msg->flags |= XPC_M_SN2_DONE;

    /*
     * The preceding store of msg->flags must occur before the following
     * load of local_GP->get.
     */
    smp_mb();

    /*
     * See if this message is next in line to be acknowledged as having
     * been delivered.
     */
    get = ch->sn.sn2.local_GP->get;
    if (get == msg_number)
        xpc_acknowledge_msgs_sn2(ch, get, msg->flags);
}

static struct xpc_arch_operations xpc_arch_ops_sn2 = {
    .setup_partitions = xpc_setup_partitions_sn2,
    .teardown_partitions = xpc_teardown_partitions_sn2,
    .process_activate_IRQ_rcvd = xpc_process_activate_IRQ_rcvd_sn2,
    .get_partition_rsvd_page_pa = xpc_get_partition_rsvd_page_pa_sn2,
    .setup_rsvd_page = xpc_setup_rsvd_page_sn2,

    .allow_hb = xpc_allow_hb_sn2,
    .disallow_hb = xpc_disallow_hb_sn2,
    .disallow_all_hbs = xpc_disallow_all_hbs_sn2,
    .increment_heartbeat = xpc_increment_heartbeat_sn2,
    .offline_heartbeat = xpc_offline_heartbeat_sn2,
    .online_heartbeat = xpc_online_heartbeat_sn2,
    .heartbeat_init = xpc_heartbeat_init_sn2,
    .heartbeat_exit = xpc_heartbeat_exit_sn2,
    .get_remote_heartbeat = xpc_get_remote_heartbeat_sn2,

    .request_partition_activation =
        xpc_request_partition_activation_sn2,
    .request_partition_reactivation =
        xpc_request_partition_reactivation_sn2,
    .request_partition_deactivation =
        xpc_request_partition_deactivation_sn2,
    .cancel_partition_deactivation_request =
        xpc_cancel_partition_deactivation_request_sn2,

    .setup_ch_structures = xpc_setup_ch_structures_sn2,
    .teardown_ch_structures = xpc_teardown_ch_structures_sn2,

    .make_first_contact = xpc_make_first_contact_sn2,

    .get_chctl_all_flags = xpc_get_chctl_all_flags_sn2,
    .send_chctl_closerequest = xpc_send_chctl_closerequest_sn2,
    .send_chctl_closereply = xpc_send_chctl_closereply_sn2,
    .send_chctl_openrequest = xpc_send_chctl_openrequest_sn2,
    .send_chctl_openreply = xpc_send_chctl_openreply_sn2,
    .send_chctl_opencomplete = xpc_send_chctl_opencomplete_sn2,
    .process_msg_chctl_flags = xpc_process_msg_chctl_flags_sn2,

    .save_remote_msgqueue_pa = xpc_save_remote_msgqueue_pa_sn2,

    .setup_msg_structures = xpc_setup_msg_structures_sn2,
    .teardown_msg_structures = xpc_teardown_msg_structures_sn2,

    .indicate_partition_engaged = xpc_indicate_partition_engaged_sn2,
    .indicate_partition_disengaged = xpc_indicate_partition_disengaged_sn2,
    .partition_engaged = xpc_partition_engaged_sn2,
    .any_partition_engaged = xpc_any_partition_engaged_sn2,
    .assume_partition_disengaged = xpc_assume_partition_disengaged_sn2,

    .n_of_deliverable_payloads = xpc_n_of_deliverable_payloads_sn2,
    .send_payload = xpc_send_payload_sn2,
    .get_deliverable_payload = xpc_get_deliverable_payload_sn2,
    .received_payload = xpc_received_payload_sn2,
    .notify_senders_of_disconnect = xpc_notify_senders_of_disconnect_sn2,
};

int
xpc_init_sn2(void)
{
    int ret;
    size_t buf_size;

    xpc_arch_ops = xpc_arch_ops_sn2;

    if (offsetof(struct xpc_msg_sn2, payload) > XPC_MSG_HDR_MAX_SIZE) {
        dev_err(xpc_part, "header portion of struct xpc_msg_sn2 is "
            "larger than %d\n", XPC_MSG_HDR_MAX_SIZE);
        return -E2BIG;
    }

    buf_size = max(XPC_RP_VARS_SIZE,
               XPC_RP_HEADER_SIZE + XP_NASID_MASK_BYTES_SN2);
    xpc_remote_copy_buffer_sn2 = xpc_kmalloc_cacheline_aligned(buf_size,
                                   GFP_KERNEL,
                          &xpc_remote_copy_buffer_base_sn2);
    if (xpc_remote_copy_buffer_sn2 == NULL) {
        dev_err(xpc_part, "can't get memory for remote copy buffer\n");
        return -ENOMEM;
    }

    /* open up protections for IPI and [potentially] amo operations */
    xpc_allow_IPI_ops_sn2();
    xpc_allow_amo_ops_shub_wars_1_1_sn2();

    /*
     * This is safe to do before the xpc_hb_checker thread has started
     * because the handler releases a wait queue.  If an interrupt is
     * received before the thread is waiting, it will not go to sleep,
     * but rather immediately process the interrupt.
     */
    ret = request_irq(SGI_XPC_ACTIVATE, xpc_handle_activate_IRQ_sn2, 0,
              "xpc hb", NULL);
    if (ret != 0) {
        dev_err(xpc_part, "can't register ACTIVATE IRQ handler, "
            "errno=%d\n", -ret);
        xpc_disallow_IPI_ops_sn2();
        kfree(xpc_remote_copy_buffer_base_sn2);
    }
    return ret;
}

void
xpc_exit_sn2(void)
{
    free_irq(SGI_XPC_ACTIVATE, NULL);
    xpc_disallow_IPI_ops_sn2();
    kfree(xpc_remote_copy_buffer_base_sn2);
}