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linux/arch/powerpc/platforms/cell/spufs/fault.c
Andre Detsch 18789fb1c3 [POWERPC] spufs: DMA Restart after SIGSEGV
This fixes the behavior of spufs when a spu tries a DMA operation
based on a wrong / unavailable address.

Instead of just generating a SIGBUS signal, spufs now
generates a SIGSEGV signal and restarts the problematic DMA operation
after the execution of the application's signal handler.  This allows
applications to employ user-level paging systems.

Although the restart_dma function is called before the application's
signal handler, the operation is not actually performed at this time,
since the spu context is already stopped.  The operation only takes
place when spu_run is restarted (which happens automatically).

Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-12-21 19:46:21 +11:00

192 lines
5.1 KiB
C

/*
* Low-level SPU handling
*
* (C) Copyright IBM Deutschland Entwicklung GmbH 2005
*
* Author: Arnd Bergmann <arndb@de.ibm.com>
*
* 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 <linux/module.h>
#include <asm/spu.h>
#include <asm/spu_csa.h>
#include "spufs.h"
/**
* Handle an SPE event, depending on context SPU_CREATE_EVENTS_ENABLED flag.
*
* If the context was created with events, we just set the return event.
* Otherwise, send an appropriate signal to the process.
*/
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.dar, SPE_EVENT_DMA_ALIGNMENT);
if (stat & CLASS0_INVALID_DMA_COMMAND_INTR)
spufs_handle_event(ctx, ctx->csa.dar, SPE_EVENT_INVALID_DMA);
if (stat & CLASS0_SPU_ERROR_INTR)
spufs_handle_event(ctx, ctx->csa.dar, SPE_EVENT_SPE_ERROR);
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, ret2;
/*
* 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.dar;
dsisr = ctx->csa.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 %016lx, dsisr %016lx 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);
/*
* If spu_acquire fails due to a pending signal we just want to return
* EINTR to userspace even if that means missing the dma restart or
* updating the page fault statistics.
*/
ret2 = spu_acquire(ctx);
if (ret2)
goto out;
/*
* 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.dar = ctx->csa.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);
out:
spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
return ret;
}