linux/drivers/gpu/drm/xe/xe_exec.c

// SPDX-License-Identifier: MIT
/*
 * Copyright © 2022 Intel Corporation
 */

#include "xe_exec.h"

#include <drm/drm_device.h>
#include <drm/drm_exec.h>
#include <drm/drm_file.h>
#include <uapi/drm/xe_drm.h>
#include <linux/delay.h>

#include "xe_device.h"
#include "xe_exec_queue.h"
#include "xe_hw_engine_group.h"
#include "xe_macros.h"
#include "xe_pm.h"
#include "xe_ring_ops_types.h"
#include "xe_sched_job.h"
#include "xe_sync.h"
#include "xe_svm.h"
#include "xe_trace.h"
#include "xe_vm.h"

/**
 * DOC: Execbuf (User GPU command submission)
 *
 * Execs have historically been rather complicated in DRM drivers (at least in
 * the i915) because a few things:
 *
 * - Passing in a list BO which are read / written to creating implicit syncs
 * - Binding at exec time
 * - Flow controlling the ring at exec time
 *
 * In Xe we avoid all of this complication by not allowing a BO list to be
 * passed into an exec, using the dma-buf implicit sync uAPI, have binds as
 * separate operations, and using the DRM scheduler to flow control the ring.
 * Let's deep dive on each of these.
 *
 * We can get away from a BO list by forcing the user to use in / out fences on
 * every exec rather than the kernel tracking dependencies of BO (e.g. if the
 * user knows an exec writes to a BO and reads from the BO in the next exec, it
 * is the user's responsibility to pass in / out fence between the two execs).
 *
 * We do not allow a user to trigger a bind at exec time rather we have a VM
 * bind IOCTL which uses the same in / out fence interface as exec. In that
 * sense, a VM bind is basically the same operation as an exec from the user
 * perspective. e.g. If an exec depends on a VM bind use the in / out fence
 * interface (struct drm_xe_sync) to synchronize like syncing between two
 * dependent execs.
 *
 * Although a user cannot trigger a bind, we still have to rebind userptrs in
 * the VM that have been invalidated since the last exec, likewise we also have
 * to rebind BOs that have been evicted by the kernel. We schedule these rebinds
 * behind any pending kernel operations on any external BOs in VM or any BOs
 * private to the VM. This is accomplished by the rebinds waiting on BOs
 * DMA_RESV_USAGE_KERNEL slot (kernel ops) and kernel ops waiting on all BOs
 * slots (inflight execs are in the DMA_RESV_USAGE_BOOKKEEP for private BOs and
 * for external BOs).
 *
 * Rebinds / dma-resv usage applies to non-compute mode VMs only as for compute
 * mode VMs we use preempt fences and a rebind worker (TODO: add link).
 *
 * There is no need to flow control the ring in the exec as we write the ring at
 * submission time and set the DRM scheduler max job limit SIZE_OF_RING /
 * MAX_JOB_SIZE. The DRM scheduler will then hold all jobs until space in the
 * ring is available.
 *
 * All of this results in a rather simple exec implementation.
 *
 * Flow
 * ~~~~
 *
 * .. code-block::
 *
 *	Parse input arguments
 *	Wait for any async VM bind passed as in-fences to start
 *	<----------------------------------------------------------------------|
 *	Lock global VM lock in read mode                                       |
 *	Pin userptrs (also finds userptr invalidated since last exec)          |
 *	Lock exec (VM dma-resv lock, external BOs dma-resv locks)              |
 *	Validate BOs that have been evicted                                    |
 *	Create job                                                             |
 *	Rebind invalidated userptrs + evicted BOs (non-compute-mode)           |
 *	Add rebind fence dependency to job                                     |
 *	Add job VM dma-resv bookkeeping slot (non-compute mode)                |
 *	Add job to external BOs dma-resv write slots (non-compute mode)        |
 *	Check if any userptrs invalidated since pin ------ Drop locks ---------|
 *	Install in / out fences for job
 *	Submit job
 *	Unlock all
 */

/*
 * Add validation and rebinding to the drm_exec locking loop, since both can
 * trigger eviction which may require sleeping dma_resv locks.
 */
static int xe_exec_fn(struct drm_gpuvm_exec *vm_exec)
{
	struct xe_vm *vm = container_of(vm_exec->vm, struct xe_vm, gpuvm);
	int ret;

	/* The fence slot added here is intended for the exec sched job. */
	xe_vm_set_validation_exec(vm, &vm_exec->exec);
	ret = xe_vm_validate_rebind(vm, &vm_exec->exec, 1);
	xe_vm_set_validation_exec(vm, NULL);
	return ret;
}

int xe_exec_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
{
	struct xe_device *xe = to_xe_device(dev);
	struct xe_file *xef = to_xe_file(file);
	struct drm_xe_exec *args = data;
	struct drm_xe_sync __user *syncs_user = u64_to_user_ptr(args->syncs);
	u64 __user *addresses_user = u64_to_user_ptr(args->address);
	struct xe_exec_queue *q;
	struct xe_sync_entry *syncs = NULL;
	u64 addresses[XE_HW_ENGINE_MAX_INSTANCE];
	struct drm_gpuvm_exec vm_exec = {.extra.fn = xe_exec_fn};
	struct drm_exec *exec = &vm_exec.exec;
	u32 i, num_syncs, num_in_sync = 0, num_ufence = 0;
	struct xe_validation_ctx ctx;
	struct xe_sched_job *job;
	struct xe_vm *vm;
	bool write_locked;
	int err = 0;
	struct xe_hw_engine_group *group;
	enum xe_hw_engine_group_execution_mode mode, previous_mode;

	if (XE_IOCTL_DBG(xe, args->extensions) ||
	    XE_IOCTL_DBG(xe, args->pad[0] || args->pad[1] || args->pad[2]) ||
	    XE_IOCTL_DBG(xe, args->reserved[0] || args->reserved[1]) ||
	    XE_IOCTL_DBG(xe, args->num_syncs > DRM_XE_MAX_SYNCS))
		return -EINVAL;

	q = xe_exec_queue_lookup(xef, args->exec_queue_id);
	if (XE_IOCTL_DBG(xe, !q))
		return -ENOENT;

	if (XE_IOCTL_DBG(xe, q->flags & EXEC_QUEUE_FLAG_VM)) {
		err = -EINVAL;
		goto err_exec_queue;
	}

	if (XE_IOCTL_DBG(xe, args->num_batch_buffer &&
			 q->width != args->num_batch_buffer)) {
		err = -EINVAL;
		goto err_exec_queue;
	}

	if (XE_IOCTL_DBG(xe, q->ops->reset_status(q))) {
		err = -ECANCELED;
		goto err_exec_queue;
	}

	if (atomic_read(&q->job_cnt) >= XE_MAX_JOB_COUNT_PER_EXEC_QUEUE) {
		trace_xe_exec_queue_reach_max_job_count(q, XE_MAX_JOB_COUNT_PER_EXEC_QUEUE);
		err = -EAGAIN;
		goto err_exec_queue;
	}

	if (args->num_syncs) {
		syncs = kcalloc(args->num_syncs, sizeof(*syncs), GFP_KERNEL);
		if (!syncs) {
			err = -ENOMEM;
			goto err_exec_queue;
		}
	}

	vm = q->vm;

	for (num_syncs = 0; num_syncs < args->num_syncs; num_syncs++) {
		err = xe_sync_entry_parse(xe, xef, &syncs[num_syncs],
					  &syncs_user[num_syncs], NULL, 0,
					  SYNC_PARSE_FLAG_EXEC |
					  (xe_vm_in_lr_mode(vm) ?
					   SYNC_PARSE_FLAG_LR_MODE : 0));
		if (err)
			goto err_syncs;

		if (xe_sync_is_ufence(&syncs[num_syncs]))
			num_ufence++;

		if (!num_in_sync && xe_sync_needs_wait(&syncs[num_syncs]))
			num_in_sync++;
	}

	if (XE_IOCTL_DBG(xe, num_ufence > 1)) {
		err = -EINVAL;
		goto err_syncs;
	}

	if (args->num_batch_buffer && xe_exec_queue_is_parallel(q)) {
		err = copy_from_user(addresses, addresses_user,
				     sizeof(u64) * q->width);
		if (err) {
			err = -EFAULT;
			goto err_syncs;
		}
	}

	group = q->hwe->hw_engine_group;
	mode = xe_hw_engine_group_find_exec_mode(q);

	if (mode == EXEC_MODE_DMA_FENCE) {
		err = xe_hw_engine_group_get_mode(group, mode, &previous_mode,
						  syncs, num_in_sync ?
						  num_syncs : 0);
		if (err)
			goto err_syncs;
	}

retry:
	if (!xe_vm_in_lr_mode(vm) && xe_vm_userptr_check_repin(vm)) {
		err = down_write_killable(&vm->lock);
		write_locked = true;
	} else {
		/* We don't allow execs while the VM is in error state */
		err = down_read_interruptible(&vm->lock);
		write_locked = false;
	}
	if (err)
		goto err_hw_exec_mode;

	if (write_locked) {
		err = xe_vm_userptr_pin(vm);
		downgrade_write(&vm->lock);
		write_locked = false;
		if (err)
			goto err_unlock_list;
	}

	if (!args->num_batch_buffer) {
		err = xe_vm_lock(vm, true);
		if (err)
			goto err_unlock_list;

		if (!xe_vm_in_lr_mode(vm)) {
			struct dma_fence *fence;

			fence = xe_sync_in_fence_get(syncs, num_syncs, q, vm);
			if (IS_ERR(fence)) {
				err = PTR_ERR(fence);
				xe_vm_unlock(vm);
				goto err_unlock_list;
			}
			for (i = 0; i < num_syncs; i++)
				xe_sync_entry_signal(&syncs[i], fence);
			xe_exec_queue_last_fence_set(q, vm, fence);
			dma_fence_put(fence);
		}

		xe_vm_unlock(vm);
		goto err_unlock_list;
	}

	/*
	 * It's OK to block interruptible here with the vm lock held, since
	 * on task freezing during suspend / hibernate, the call will
	 * return -ERESTARTSYS and the IOCTL will be rerun.
	 */
	err = xe_pm_block_on_suspend(xe);
	if (err)
		goto err_unlock_list;

	if (!xe_vm_in_lr_mode(vm)) {
		vm_exec.vm = &vm->gpuvm;
		vm_exec.flags = DRM_EXEC_INTERRUPTIBLE_WAIT;
		err = xe_validation_exec_lock(&ctx, &vm_exec, &xe->val);
		if (err)
			goto err_unlock_list;
	}

	if (xe_vm_is_closed_or_banned(q->vm)) {
		drm_warn(&xe->drm, "Trying to schedule after vm is closed or banned\n");
		err = -ECANCELED;
		goto err_exec;
	}

	if (xe_exec_queue_uses_pxp(q)) {
		err = xe_vm_validate_protected(q->vm);
		if (err)
			goto err_exec;
	}

	job = xe_sched_job_create(q, xe_exec_queue_is_parallel(q) ?
				  addresses : &args->address);
	if (IS_ERR(job)) {
		err = PTR_ERR(job);
		goto err_exec;
	}

	/* Wait behind rebinds */
	if (!xe_vm_in_lr_mode(vm)) {
		err = xe_sched_job_add_deps(job,
					    xe_vm_resv(vm),
					    DMA_RESV_USAGE_KERNEL);
		if (err)
			goto err_put_job;
	}

	for (i = 0; i < num_syncs && !err; i++)
		err = xe_sync_entry_add_deps(&syncs[i], job);
	if (err)
		goto err_put_job;

	if (!xe_vm_in_lr_mode(vm)) {
		err = xe_svm_notifier_lock_interruptible(vm);
		if (err)
			goto err_put_job;

		err = __xe_vm_userptr_needs_repin(vm);
		if (err)
			goto err_repin;
	}

	/*
	 * Point of no return, if we error after this point just set an error on
	 * the job and let the DRM scheduler / backend clean up the job.
	 */
	xe_sched_job_arm(job);
	if (!xe_vm_in_lr_mode(vm))
		drm_gpuvm_resv_add_fence(&vm->gpuvm, exec, &job->drm.s_fence->finished,
					 DMA_RESV_USAGE_BOOKKEEP,
					 DMA_RESV_USAGE_BOOKKEEP);

	for (i = 0; i < num_syncs; i++) {
		xe_sync_entry_signal(&syncs[i], &job->drm.s_fence->finished);
		xe_sched_job_init_user_fence(job, &syncs[i]);
	}

	if (!xe_vm_in_lr_mode(vm))
		xe_exec_queue_last_fence_set(q, vm, &job->drm.s_fence->finished);
	xe_sched_job_push(job);
	xe_vm_reactivate_rebind(vm);

	if (!err && !xe_vm_in_lr_mode(vm)) {
		spin_lock(&xe->ttm.lru_lock);
		ttm_lru_bulk_move_tail(&vm->lru_bulk_move);
		spin_unlock(&xe->ttm.lru_lock);
	}

	if (mode == EXEC_MODE_LR)
		xe_hw_engine_group_resume_faulting_lr_jobs(group);

err_repin:
	if (!xe_vm_in_lr_mode(vm))
		xe_svm_notifier_unlock(vm);
err_put_job:
	if (err)
		xe_sched_job_put(job);
err_exec:
	if (!xe_vm_in_lr_mode(vm))
		xe_validation_ctx_fini(&ctx);
err_unlock_list:
	up_read(&vm->lock);
	if (err == -EAGAIN)
		goto retry;
err_hw_exec_mode:
	if (mode == EXEC_MODE_DMA_FENCE)
		xe_hw_engine_group_put(group);
err_syncs:
	while (num_syncs--)
		xe_sync_entry_cleanup(&syncs[num_syncs]);
	kfree(syncs);
err_exec_queue:
	xe_exec_queue_put(q);

	return err;
}