fault.c

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/*
 * Low-level SPU handling
 *
 * (C) Copyright IBM Deutschland Entwicklung GmbH 2005
 *
 * Author: Arnd Bergmann <[email protected]>
 *
 * 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; either version 2, or (at your option)
 * any later version.
 *
 * 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.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
#include <linux/sched.h>
#include <linux/mm.h>

#include <asm/spu.h>
#include <asm/spu_csa.h>

#include "spufs.h"

static void spufs_handle_event(struct spu_context *ctx,
                unsigned long ea, int type)
{
    siginfo_t info;

    if (ctx->flags & SPU_CREATE_EVENTS_ENABLED) {
        ctx->event_return |= type;
        wake_up_all(&ctx->stop_wq);
        return;
    }

    memset(&info, 0, sizeof(info));

    switch (type) {
    case SPE_EVENT_INVALID_DMA:
        info.si_signo = SIGBUS;
        info.si_code = BUS_OBJERR;
        break;
    case SPE_EVENT_SPE_DATA_STORAGE:
        info.si_signo = SIGSEGV;
        info.si_addr = (void __user *)ea;
        info.si_code = SEGV_ACCERR;
        ctx->ops->restart_dma(ctx);
        break;
    case SPE_EVENT_DMA_ALIGNMENT:
        info.si_signo = SIGBUS;
        /* DAR isn't set for an alignment fault :( */
        info.si_code = BUS_ADRALN;
        break;
    case SPE_EVENT_SPE_ERROR:
        info.si_signo = SIGILL;
        info.si_addr = (void __user *)(unsigned long)
            ctx->ops->npc_read(ctx) - 4;
        info.si_code = ILL_ILLOPC;
        break;
    }

    if (info.si_signo)
        force_sig_info(info.si_signo, &info, current);
}

int spufs_handle_class0(struct spu_context *ctx)
{
    unsigned long stat = ctx->csa.class_0_pending & CLASS0_INTR_MASK;

    if (likely(!stat))
        return 0;

    if (stat & CLASS0_DMA_ALIGNMENT_INTR)
        spufs_handle_event(ctx, ctx->csa.class_0_dar,
            SPE_EVENT_DMA_ALIGNMENT);

    if (stat & CLASS0_INVALID_DMA_COMMAND_INTR)
        spufs_handle_event(ctx, ctx->csa.class_0_dar,
            SPE_EVENT_INVALID_DMA);

    if (stat & CLASS0_SPU_ERROR_INTR)
        spufs_handle_event(ctx, ctx->csa.class_0_dar,
            SPE_EVENT_SPE_ERROR);

    ctx->csa.class_0_pending = 0;

    return -EIO;
}

/*
 * bottom half handler for page faults, we can't do this from
 * interrupt context, since we might need to sleep.
 * we also need to give up the mutex so we can get scheduled
 * out while waiting for the backing store.
 *
 * TODO: try calling hash_page from the interrupt handler first
 *       in order to speed up the easy case.
 */
int spufs_handle_class1(struct spu_context *ctx)
{
    u64 ea, dsisr, access;
    unsigned long flags;
    unsigned flt = 0;
    int ret;

    /*
     * dar and dsisr get passed from the registers
     * to the spu_context, to this function, but not
     * back to the spu if it gets scheduled again.
     *
     * if we don't handle the fault for a saved context
     * in time, we can still expect to get the same fault
     * the immediately after the context restore.
     */
    ea = ctx->csa.class_1_dar;
    dsisr = ctx->csa.class_1_dsisr;

    if (!(dsisr & (MFC_DSISR_PTE_NOT_FOUND | MFC_DSISR_ACCESS_DENIED)))
        return 0;

    spuctx_switch_state(ctx, SPU_UTIL_IOWAIT);

    pr_debug("ctx %p: ea %016llx, dsisr %016llx state %d\n", ctx, ea,
        dsisr, ctx->state);

    ctx->stats.hash_flt++;
    if (ctx->state == SPU_STATE_RUNNABLE)
        ctx->spu->stats.hash_flt++;

    /* we must not hold the lock when entering spu_handle_mm_fault */
    spu_release(ctx);

    access = (_PAGE_PRESENT | _PAGE_USER);
    access |= (dsisr & MFC_DSISR_ACCESS_PUT) ? _PAGE_RW : 0UL;
    local_irq_save(flags);
    ret = hash_page(ea, access, 0x300);
    local_irq_restore(flags);

    /* hashing failed, so try the actual fault handler */
    if (ret)
        ret = spu_handle_mm_fault(current->mm, ea, dsisr, &flt);

    /*
     * This is nasty: we need the state_mutex for all the bookkeeping even
     * if the syscall was interrupted by a signal. ewww.
     */
    mutex_lock(&ctx->state_mutex);

    /*
     * Clear dsisr under ctxt lock after handling the fault, so that
     * time slicing will not preempt the context while the page fault
     * handler is running. Context switch code removes mappings.
     */
    ctx->csa.class_1_dar = ctx->csa.class_1_dsisr = 0;

    /*
     * If we handled the fault successfully and are in runnable
     * state, restart the DMA.
     * In case of unhandled error report the problem to user space.
     */
    if (!ret) {
        if (flt & VM_FAULT_MAJOR)
            ctx->stats.maj_flt++;
        else
            ctx->stats.min_flt++;
        if (ctx->state == SPU_STATE_RUNNABLE) {
            if (flt & VM_FAULT_MAJOR)
                ctx->spu->stats.maj_flt++;
            else
                ctx->spu->stats.min_flt++;
        }

        if (ctx->spu)
            ctx->ops->restart_dma(ctx);
    } else
        spufs_handle_event(ctx, ea, SPE_EVENT_SPE_DATA_STORAGE);

    spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
    return ret;
}