fault.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 = SIGBUS;
		info.si_addr = (void __user *)ea;
		info.si_code = BUS_ADRERR;
		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;

	/*
	 * 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);

	spu_acquire(ctx);

	/*
	 * 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);

	spuctx_switch_state(ctx, SPU_UTIL_SYSTEM);
	return ret;
}