messaging.c

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/*
 * Copyright 2010 Tilera Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation, version 2.
 *
 *   This program is distributed in the hope that it will be useful, but
 *   WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 *   NON INFRINGEMENT.  See the GNU General Public License for
 *   more details.
 */

#include <linux/percpu.h>
#include <linux/smp.h>
#include <linux/hardirq.h>
#include <linux/ptrace.h>
#include <asm/hv_driver.h>
#include <asm/irq_regs.h>
#include <asm/traps.h>
#include <hv/hypervisor.h>
#include <arch/interrupts.h>

/* All messages are stored here */
static DEFINE_PER_CPU(HV_MsgState, msg_state);

void __cpuinit init_messaging(void)
{
    /* Allocate storage for messages in kernel space */
    HV_MsgState *state = &__get_cpu_var(msg_state);
    int rc = hv_register_message_state(state);
    if (rc != HV_OK)
        panic("hv_register_message_state: error %d", rc);

    /* Make sure downcall interrupts will be enabled. */
    arch_local_irq_unmask(INT_INTCTRL_K);
}

void hv_message_intr(struct pt_regs *regs, int intnum)
{
    /*
     * We enter with interrupts disabled and leave them disabled,
     * to match expectations of called functions (e.g.
     * do_ccupdate_local() in mm/slab.c).  This is also consistent
     * with normal call entry for device interrupts.
     */

    int message[HV_MAX_MESSAGE_SIZE/sizeof(int)];
    HV_RcvMsgInfo rmi;
    int nmsgs = 0;

    /* Track time spent here in an interrupt context */
    struct pt_regs *old_regs = set_irq_regs(regs);
    irq_enter();

#ifdef CONFIG_DEBUG_STACKOVERFLOW
    /* Debugging check for stack overflow: less than 1/8th stack free? */
    {
        long sp = stack_pointer - (long) current_thread_info();
        if (unlikely(sp < (sizeof(struct thread_info) + STACK_WARN))) {
            pr_emerg("hv_message_intr: "
                   "stack overflow: %ld\n",
                   sp - sizeof(struct thread_info));
            dump_stack();
        }
    }
#endif

    while (1) {
        rmi = hv_receive_message(__get_cpu_var(msg_state),
                     (HV_VirtAddr) message,
                     sizeof(message));
        if (rmi.msglen == 0)
            break;

        if (rmi.msglen < 0)
            panic("hv_receive_message failed: %d", rmi.msglen);

        ++nmsgs;

        if (rmi.source == HV_MSG_TILE) {
            int tag;

            /* we just send tags for now */
            BUG_ON(rmi.msglen != sizeof(int));

            tag = message[0];
#ifdef CONFIG_SMP
            evaluate_message(message[0]);
#else
            panic("Received IPI message %d in UP mode", tag);
#endif
        } else if (rmi.source == HV_MSG_INTR) {
            HV_IntrMsg *him = (HV_IntrMsg *)message;
            struct hv_driver_cb *cb =
                (struct hv_driver_cb *)him->intarg;
            cb->callback(cb, him->intdata);
            __get_cpu_var(irq_stat).irq_hv_msg_count++;
        }
    }

    /*
     * We shouldn't have gotten a message downcall with no
     * messages available.
     */
    if (nmsgs == 0)
        panic("Message downcall invoked with no messages!");

    /*
     * Track time spent against the current process again and
     * process any softirqs if they are waiting.
     */
    irq_exit();
    set_irq_regs(old_regs);
}