i915/gvt/scheduler.c

/*
 * Copyright(c) 2011-2016 Intel Corporation. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 * Authors:
 *    Zhi Wang <zhi.a.wang@intel.com>
 *
 * Contributors:
 *    Ping Gao <ping.a.gao@intel.com>
 *    Tina Zhang <tina.zhang@intel.com>
 *    Chanbin Du <changbin.du@intel.com>
 *    Min He <min.he@intel.com>
 *    Bing Niu <bing.niu@intel.com>
 *    Zhenyu Wang <zhenyuw@linux.intel.com>
 *
 */

#include <linux/kthread.h>

#include "i915_drv.h"
#include "gvt.h"

#define RING_CTX_OFF(x) \
	offsetof(struct execlist_ring_context, x)

static void set_context_pdp_root_pointer(
		struct execlist_ring_context *ring_context,
		u32 pdp[8])
{
	int i;

	for (i = 0; i < 8; i++)
		ring_context->pdps[i].val = pdp[7 - i];
}

static void update_shadow_pdps(struct intel_vgpu_workload *workload)
{
	struct drm_i915_gem_object *ctx_obj =
		workload->req->hw_context->state->obj;
	struct execlist_ring_context *shadow_ring_context;
	struct page *page;

	if (WARN_ON(!workload->shadow_mm))
		return;

	if (WARN_ON(!atomic_read(&workload->shadow_mm->pincount)))
		return;

	page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
	shadow_ring_context = kmap(page);
	set_context_pdp_root_pointer(shadow_ring_context,
			(void *)workload->shadow_mm->ppgtt_mm.shadow_pdps);
	kunmap(page);
}

/*
 * when populating shadow ctx from guest, we should not overrride oa related
 * registers, so that they will not be overlapped by guest oa configs. Thus
 * made it possible to capture oa data from host for both host and guests.
 */
static void sr_oa_regs(struct intel_vgpu_workload *workload,
		u32 *reg_state, bool save)
{
	struct drm_i915_private *dev_priv = workload->vgpu->gvt->dev_priv;
	u32 ctx_oactxctrl = dev_priv->perf.oa.ctx_oactxctrl_offset;
	u32 ctx_flexeu0 = dev_priv->perf.oa.ctx_flexeu0_offset;
	int i = 0;
	u32 flex_mmio[] = {
		i915_mmio_reg_offset(EU_PERF_CNTL0),
		i915_mmio_reg_offset(EU_PERF_CNTL1),
		i915_mmio_reg_offset(EU_PERF_CNTL2),
		i915_mmio_reg_offset(EU_PERF_CNTL3),
		i915_mmio_reg_offset(EU_PERF_CNTL4),
		i915_mmio_reg_offset(EU_PERF_CNTL5),
		i915_mmio_reg_offset(EU_PERF_CNTL6),
	};

	if (workload->ring_id != RCS)
		return;

	if (save) {
		workload->oactxctrl = reg_state[ctx_oactxctrl + 1];

		for (i = 0; i < ARRAY_SIZE(workload->flex_mmio); i++) {
			u32 state_offset = ctx_flexeu0 + i * 2;

			workload->flex_mmio[i] = reg_state[state_offset + 1];
		}
	} else {
		reg_state[ctx_oactxctrl] =
			i915_mmio_reg_offset(GEN8_OACTXCONTROL);
		reg_state[ctx_oactxctrl + 1] = workload->oactxctrl;

		for (i = 0; i < ARRAY_SIZE(workload->flex_mmio); i++) {
			u32 state_offset = ctx_flexeu0 + i * 2;
			u32 mmio = flex_mmio[i];

			reg_state[state_offset] = mmio;
			reg_state[state_offset + 1] = workload->flex_mmio[i];
		}
	}
}

static int populate_shadow_context(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct intel_gvt *gvt = vgpu->gvt;
	int ring_id = workload->ring_id;
	struct drm_i915_gem_object *ctx_obj =
		workload->req->hw_context->state->obj;
	struct execlist_ring_context *shadow_ring_context;
	struct page *page;
	void *dst;
	unsigned long context_gpa, context_page_num;
	int i;

	page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
	shadow_ring_context = kmap(page);

	sr_oa_regs(workload, (u32 *)shadow_ring_context, true);
#define COPY_REG(name) \
	intel_gvt_hypervisor_read_gpa(vgpu, workload->ring_context_gpa \
		+ RING_CTX_OFF(name.val), &shadow_ring_context->name.val, 4)
#define COPY_REG_MASKED(name) {\
		intel_gvt_hypervisor_read_gpa(vgpu, workload->ring_context_gpa \
					      + RING_CTX_OFF(name.val),\
					      &shadow_ring_context->name.val, 4);\
		shadow_ring_context->name.val |= 0xffff << 16;\
	}

	COPY_REG_MASKED(ctx_ctrl);
	COPY_REG(ctx_timestamp);

	if (ring_id == RCS) {
		COPY_REG(bb_per_ctx_ptr);
		COPY_REG(rcs_indirect_ctx);
		COPY_REG(rcs_indirect_ctx_offset);
	}
#undef COPY_REG
#undef COPY_REG_MASKED

	intel_gvt_hypervisor_read_gpa(vgpu,
			workload->ring_context_gpa +
			sizeof(*shadow_ring_context),
			(void *)shadow_ring_context +
			sizeof(*shadow_ring_context),
			I915_GTT_PAGE_SIZE - sizeof(*shadow_ring_context));

	sr_oa_regs(workload, (u32 *)shadow_ring_context, false);
	kunmap(page);

	if (IS_RESTORE_INHIBIT(shadow_ring_context->ctx_ctrl.val))
		return 0;

	gvt_dbg_sched("ring id %d workload lrca %x", ring_id,
			workload->ctx_desc.lrca);

	context_page_num = gvt->dev_priv->engine[ring_id]->context_size;

	context_page_num = context_page_num >> PAGE_SHIFT;

	if (IS_BROADWELL(gvt->dev_priv) && ring_id == RCS)
		context_page_num = 19;

	i = 2;
	while (i < context_page_num) {
		context_gpa = intel_vgpu_gma_to_gpa(vgpu->gtt.ggtt_mm,
				(u32)((workload->ctx_desc.lrca + i) <<
				I915_GTT_PAGE_SHIFT));
		if (context_gpa == INTEL_GVT_INVALID_ADDR) {
			gvt_vgpu_err("Invalid guest context descriptor\n");
			return -EFAULT;
		}

		page = i915_gem_object_get_page(ctx_obj, LRC_HEADER_PAGES + i);
		dst = kmap(page);
		intel_gvt_hypervisor_read_gpa(vgpu, context_gpa, dst,
				I915_GTT_PAGE_SIZE);
		kunmap(page);
		i++;
	}
	return 0;
}

static inline bool is_gvt_request(struct i915_request *req)
{
	return i915_gem_context_force_single_submission(req->gem_context);
}

static void save_ring_hw_state(struct intel_vgpu *vgpu, int ring_id)
{
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	u32 ring_base = dev_priv->engine[ring_id]->mmio_base;
	i915_reg_t reg;

	reg = RING_INSTDONE(ring_base);
	vgpu_vreg(vgpu, i915_mmio_reg_offset(reg)) = I915_READ_FW(reg);
	reg = RING_ACTHD(ring_base);
	vgpu_vreg(vgpu, i915_mmio_reg_offset(reg)) = I915_READ_FW(reg);
	reg = RING_ACTHD_UDW(ring_base);
	vgpu_vreg(vgpu, i915_mmio_reg_offset(reg)) = I915_READ_FW(reg);
}

static int shadow_context_status_change(struct notifier_block *nb,
		unsigned long action, void *data)
{
	struct i915_request *req = data;
	struct intel_gvt *gvt = container_of(nb, struct intel_gvt,
				shadow_ctx_notifier_block[req->engine->id]);
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	enum intel_engine_id ring_id = req->engine->id;
	struct intel_vgpu_workload *workload;
	unsigned long flags;

	if (!is_gvt_request(req)) {
		spin_lock_irqsave(&scheduler->mmio_context_lock, flags);
		if (action == INTEL_CONTEXT_SCHEDULE_IN &&
		    scheduler->engine_owner[ring_id]) {
			/* Switch ring from vGPU to host. */
			intel_gvt_switch_mmio(scheduler->engine_owner[ring_id],
					      NULL, ring_id);
			scheduler->engine_owner[ring_id] = NULL;
		}
		spin_unlock_irqrestore(&scheduler->mmio_context_lock, flags);

		return NOTIFY_OK;
	}

	workload = scheduler->current_workload[ring_id];
	if (unlikely(!workload))
		return NOTIFY_OK;

	switch (action) {
	case INTEL_CONTEXT_SCHEDULE_IN:
		spin_lock_irqsave(&scheduler->mmio_context_lock, flags);
		if (workload->vgpu != scheduler->engine_owner[ring_id]) {
			/* Switch ring from host to vGPU or vGPU to vGPU. */
			intel_gvt_switch_mmio(scheduler->engine_owner[ring_id],
					      workload->vgpu, ring_id);
			scheduler->engine_owner[ring_id] = workload->vgpu;
		} else
			gvt_dbg_sched("skip ring %d mmio switch for vgpu%d\n",
				      ring_id, workload->vgpu->id);
		spin_unlock_irqrestore(&scheduler->mmio_context_lock, flags);
		atomic_set(&workload->shadow_ctx_active, 1);
		break;
	case INTEL_CONTEXT_SCHEDULE_OUT:
		save_ring_hw_state(workload->vgpu, ring_id);
		atomic_set(&workload->shadow_ctx_active, 0);
		break;
	case INTEL_CONTEXT_SCHEDULE_PREEMPTED:
		save_ring_hw_state(workload->vgpu, ring_id);
		break;
	default:
		WARN_ON(1);
		return NOTIFY_OK;
	}
	wake_up(&workload->shadow_ctx_status_wq);
	return NOTIFY_OK;
}

static void shadow_context_descriptor_update(struct intel_context *ce)
{
	u64 desc = 0;

	desc = ce->lrc_desc;

	/* Update bits 0-11 of the context descriptor which includes flags
	 * like GEN8_CTX_* cached in desc_template
	 */
	desc &= U64_MAX << 12;
	desc |= ce->gem_context->desc_template & ((1ULL << 12) - 1);

	ce->lrc_desc = desc;
}

static int copy_workload_to_ring_buffer(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct i915_request *req = workload->req;
	void *shadow_ring_buffer_va;
	u32 *cs;

	if ((IS_KABYLAKE(req->i915) || IS_BROXTON(req->i915)
		|| IS_COFFEELAKE(req->i915))
		&& is_inhibit_context(req->hw_context))
		intel_vgpu_restore_inhibit_context(vgpu, req);

	/* allocate shadow ring buffer */
	cs = intel_ring_begin(workload->req, workload->rb_len / sizeof(u32));
	if (IS_ERR(cs)) {
		gvt_vgpu_err("fail to alloc size =%ld shadow  ring buffer\n",
			workload->rb_len);
		return PTR_ERR(cs);
	}

	shadow_ring_buffer_va = workload->shadow_ring_buffer_va;

	/* get shadow ring buffer va */
	workload->shadow_ring_buffer_va = cs;

	memcpy(cs, shadow_ring_buffer_va,
			workload->rb_len);

	cs += workload->rb_len / sizeof(u32);
	intel_ring_advance(workload->req, cs);

	return 0;
}

static void release_shadow_wa_ctx(struct intel_shadow_wa_ctx *wa_ctx)
{
	if (!wa_ctx->indirect_ctx.obj)
		return;

	i915_gem_object_unpin_map(wa_ctx->indirect_ctx.obj);
	i915_gem_object_put(wa_ctx->indirect_ctx.obj);

	wa_ctx->indirect_ctx.obj = NULL;
	wa_ctx->indirect_ctx.shadow_va = NULL;
}

static int set_context_ppgtt_from_shadow(struct intel_vgpu_workload *workload,
					 struct i915_gem_context *ctx)
{
	struct intel_vgpu_mm *mm = workload->shadow_mm;
	struct i915_hw_ppgtt *ppgtt = ctx->ppgtt;
	int i = 0;

	if (mm->type != INTEL_GVT_MM_PPGTT || !mm->ppgtt_mm.shadowed)
		return -EINVAL;

	if (mm->ppgtt_mm.root_entry_type == GTT_TYPE_PPGTT_ROOT_L4_ENTRY) {
		px_dma(&ppgtt->pml4) = mm->ppgtt_mm.shadow_pdps[0];
	} else {
		for (i = 0; i < GVT_RING_CTX_NR_PDPS; i++) {
			px_dma(ppgtt->pdp.page_directory[i]) =
				mm->ppgtt_mm.shadow_pdps[i];
		}
	}

	return 0;
}

static int
intel_gvt_workload_req_alloc(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct i915_gem_context *shadow_ctx = s->shadow_ctx;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	struct intel_engine_cs *engine = dev_priv->engine[workload->ring_id];
	struct i915_request *rq;
	int ret = 0;

	lockdep_assert_held(&dev_priv->drm.struct_mutex);

	if (workload->req)
		goto out;

	rq = i915_request_alloc(engine, shadow_ctx);
	if (IS_ERR(rq)) {
		gvt_vgpu_err("fail to allocate gem request\n");
		ret = PTR_ERR(rq);
		goto out;
	}
	workload->req = i915_request_get(rq);
out:
	return ret;
}

/**
 * intel_gvt_scan_and_shadow_workload - audit the workload by scanning and
 * shadow it as well, include ringbuffer,wa_ctx and ctx.
 * @workload: an abstract entity for each execlist submission.
 *
 * This function is called before the workload submitting to i915, to make
 * sure the content of the workload is valid.
 */
int intel_gvt_scan_and_shadow_workload(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct i915_gem_context *shadow_ctx = s->shadow_ctx;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	struct intel_engine_cs *engine = dev_priv->engine[workload->ring_id];
	struct intel_context *ce;
	int ret;

	lockdep_assert_held(&dev_priv->drm.struct_mutex);

	if (workload->shadow)
		return 0;

	/* pin shadow context by gvt even the shadow context will be pinned
	 * when i915 alloc request. That is because gvt will update the guest
	 * context from shadow context when workload is completed, and at that
	 * moment, i915 may already unpined the shadow context to make the
	 * shadow_ctx pages invalid. So gvt need to pin itself. After update
	 * the guest context, gvt can unpin the shadow_ctx safely.
	 */
	ce = intel_context_pin(shadow_ctx, engine);
	if (IS_ERR(ce)) {
		gvt_vgpu_err("fail to pin shadow context\n");
		return PTR_ERR(ce);
	}

	shadow_ctx->desc_template &= ~(0x3 << GEN8_CTX_ADDRESSING_MODE_SHIFT);
	shadow_ctx->desc_template |= workload->ctx_desc.addressing_mode <<
				    GEN8_CTX_ADDRESSING_MODE_SHIFT;

	if (!test_and_set_bit(workload->ring_id, s->shadow_ctx_desc_updated))
		shadow_context_descriptor_update(ce);

	ret = intel_gvt_scan_and_shadow_ringbuffer(workload);
	if (ret)
		goto err_unpin;

	if ((workload->ring_id == RCS) &&
	    (workload->wa_ctx.indirect_ctx.size != 0)) {
		ret = intel_gvt_scan_and_shadow_wa_ctx(&workload->wa_ctx);
		if (ret)
			goto err_shadow;
	}

	workload->shadow = true;
	return 0;
err_shadow:
	release_shadow_wa_ctx(&workload->wa_ctx);
err_unpin:
	intel_context_unpin(ce);
	return ret;
}

static void release_shadow_batch_buffer(struct intel_vgpu_workload *workload);

static int prepare_shadow_batch_buffer(struct intel_vgpu_workload *workload)
{
	struct intel_gvt *gvt = workload->vgpu->gvt;
	const int gmadr_bytes = gvt->device_info.gmadr_bytes_in_cmd;
	struct intel_vgpu_shadow_bb *bb;
	int ret;

	list_for_each_entry(bb, &workload->shadow_bb, list) {
		/* For privilge batch buffer and not wa_ctx, the bb_start_cmd_va
		 * is only updated into ring_scan_buffer, not real ring address
		 * allocated in later copy_workload_to_ring_buffer. pls be noted
		 * shadow_ring_buffer_va is now pointed to real ring buffer va
		 * in copy_workload_to_ring_buffer.
		 */

		if (bb->bb_offset)
			bb->bb_start_cmd_va = workload->shadow_ring_buffer_va
				+ bb->bb_offset;

		if (bb->ppgtt) {
			/* for non-priv bb, scan&shadow is only for
			 * debugging purpose, so the content of shadow bb
			 * is the same as original bb. Therefore,
			 * here, rather than switch to shadow bb's gma
			 * address, we directly use original batch buffer's
			 * gma address, and send original bb to hardware
			 * directly
			 */
			if (bb->clflush & CLFLUSH_AFTER) {
				drm_clflush_virt_range(bb->va,
						bb->obj->base.size);
				bb->clflush &= ~CLFLUSH_AFTER;
			}
			i915_gem_obj_finish_shmem_access(bb->obj);
			bb->accessing = false;

		} else {
			bb->vma = i915_gem_object_ggtt_pin(bb->obj,
					NULL, 0, 0, 0);
			if (IS_ERR(bb->vma)) {
				ret = PTR_ERR(bb->vma);
				goto err;
			}

			/* relocate shadow batch buffer */
			bb->bb_start_cmd_va[1] = i915_ggtt_offset(bb->vma);
			if (gmadr_bytes == 8)
				bb->bb_start_cmd_va[2] = 0;

			/* No one is going to touch shadow bb from now on. */
			if (bb->clflush & CLFLUSH_AFTER) {
				drm_clflush_virt_range(bb->va,
						bb->obj->base.size);
				bb->clflush &= ~CLFLUSH_AFTER;
			}

			ret = i915_gem_object_set_to_gtt_domain(bb->obj,
					false);
			if (ret)
				goto err;

			i915_gem_obj_finish_shmem_access(bb->obj);
			bb->accessing = false;

			ret = i915_vma_move_to_active(bb->vma,
						      workload->req,
						      0);
			if (ret)
				goto err;
		}
	}
	return 0;
err:
	release_shadow_batch_buffer(workload);
	return ret;
}

static void update_wa_ctx_2_shadow_ctx(struct intel_shadow_wa_ctx *wa_ctx)
{
	struct intel_vgpu_workload *workload =
		container_of(wa_ctx, struct intel_vgpu_workload, wa_ctx);
	struct i915_request *rq = workload->req;
	struct execlist_ring_context *shadow_ring_context =
		(struct execlist_ring_context *)rq->hw_context->lrc_reg_state;

	shadow_ring_context->bb_per_ctx_ptr.val =
		(shadow_ring_context->bb_per_ctx_ptr.val &
		(~PER_CTX_ADDR_MASK)) | wa_ctx->per_ctx.shadow_gma;
	shadow_ring_context->rcs_indirect_ctx.val =
		(shadow_ring_context->rcs_indirect_ctx.val &
		(~INDIRECT_CTX_ADDR_MASK)) | wa_ctx->indirect_ctx.shadow_gma;
}

static int prepare_shadow_wa_ctx(struct intel_shadow_wa_ctx *wa_ctx)
{
	struct i915_vma *vma;
	unsigned char *per_ctx_va =
		(unsigned char *)wa_ctx->indirect_ctx.shadow_va +
		wa_ctx->indirect_ctx.size;

	if (wa_ctx->indirect_ctx.size == 0)
		return 0;

	vma = i915_gem_object_ggtt_pin(wa_ctx->indirect_ctx.obj, NULL,
				       0, CACHELINE_BYTES, 0);
	if (IS_ERR(vma))
		return PTR_ERR(vma);

	/* FIXME: we are not tracking our pinned VMA leaving it
	 * up to the core to fix up the stray pin_count upon
	 * free.
	 */

	wa_ctx->indirect_ctx.shadow_gma = i915_ggtt_offset(vma);

	wa_ctx->per_ctx.shadow_gma = *((unsigned int *)per_ctx_va + 1);
	memset(per_ctx_va, 0, CACHELINE_BYTES);

	update_wa_ctx_2_shadow_ctx(wa_ctx);
	return 0;
}

static void release_shadow_batch_buffer(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	struct intel_vgpu_shadow_bb *bb, *pos;

	if (list_empty(&workload->shadow_bb))
		return;

	bb = list_first_entry(&workload->shadow_bb,
			struct intel_vgpu_shadow_bb, list);

	mutex_lock(&dev_priv->drm.struct_mutex);

	list_for_each_entry_safe(bb, pos, &workload->shadow_bb, list) {
		if (bb->obj) {
			if (bb->accessing)
				i915_gem_obj_finish_shmem_access(bb->obj);

			if (bb->va && !IS_ERR(bb->va))
				i915_gem_object_unpin_map(bb->obj);

			if (bb->vma && !IS_ERR(bb->vma)) {
				i915_vma_unpin(bb->vma);
				i915_vma_close(bb->vma);
			}
			__i915_gem_object_release_unless_active(bb->obj);
		}
		list_del(&bb->list);
		kfree(bb);
	}

	mutex_unlock(&dev_priv->drm.struct_mutex);
}

static int prepare_workload(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	int ret = 0;

	ret = intel_vgpu_pin_mm(workload->shadow_mm);
	if (ret) {
		gvt_vgpu_err("fail to vgpu pin mm\n");
		return ret;
	}

	update_shadow_pdps(workload);

	ret = intel_vgpu_sync_oos_pages(workload->vgpu);
	if (ret) {
		gvt_vgpu_err("fail to vgpu sync oos pages\n");
		goto err_unpin_mm;
	}

	ret = intel_vgpu_flush_post_shadow(workload->vgpu);
	if (ret) {
		gvt_vgpu_err("fail to flush post shadow\n");
		goto err_unpin_mm;
	}

	ret = copy_workload_to_ring_buffer(workload);
	if (ret) {
		gvt_vgpu_err("fail to generate request\n");
		goto err_unpin_mm;
	}

	ret = prepare_shadow_batch_buffer(workload);
	if (ret) {
		gvt_vgpu_err("fail to prepare_shadow_batch_buffer\n");
		goto err_unpin_mm;
	}

	ret = prepare_shadow_wa_ctx(&workload->wa_ctx);
	if (ret) {
		gvt_vgpu_err("fail to prepare_shadow_wa_ctx\n");
		goto err_shadow_batch;
	}

	if (workload->prepare) {
		ret = workload->prepare(workload);
		if (ret)
			goto err_shadow_wa_ctx;
	}

	return 0;
err_shadow_wa_ctx:
	release_shadow_wa_ctx(&workload->wa_ctx);
err_shadow_batch:
	release_shadow_batch_buffer(workload);
err_unpin_mm:
	intel_vgpu_unpin_mm(workload->shadow_mm);
	return ret;
}

static int dispatch_workload(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu *vgpu = workload->vgpu;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct i915_gem_context *shadow_ctx = s->shadow_ctx;
	struct i915_request *rq;
	int ring_id = workload->ring_id;
	int ret;

	gvt_dbg_sched("ring id %d prepare to dispatch workload %p\n",
		ring_id, workload);

	mutex_lock(&vgpu->vgpu_lock);
	mutex_lock(&dev_priv->drm.struct_mutex);

	ret = set_context_ppgtt_from_shadow(workload, shadow_ctx);
	if (ret < 0) {
		gvt_vgpu_err("workload shadow ppgtt isn't ready\n");
		goto err_req;
	}

	ret = intel_gvt_workload_req_alloc(workload);
	if (ret)
		goto err_req;

	ret = intel_gvt_scan_and_shadow_workload(workload);
	if (ret)
		goto out;

	ret = populate_shadow_context(workload);
	if (ret) {
		release_shadow_wa_ctx(&workload->wa_ctx);
		goto out;
	}

	ret = prepare_workload(workload);
out:
	if (ret) {
		/* We might still need to add request with
		 * clean ctx to retire it properly..
		 */
		rq = fetch_and_zero(&workload->req);
		i915_request_put(rq);
	}

	if (!IS_ERR_OR_NULL(workload->req)) {
		gvt_dbg_sched("ring id %d submit workload to i915 %p\n",
				ring_id, workload->req);
		i915_request_add(workload->req);
		workload->dispatched = true;
	}
err_req:
	if (ret)
		workload->status = ret;
	mutex_unlock(&dev_priv->drm.struct_mutex);
	mutex_unlock(&vgpu->vgpu_lock);
	return ret;
}

static struct intel_vgpu_workload *pick_next_workload(
		struct intel_gvt *gvt, int ring_id)
{
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	struct intel_vgpu_workload *workload = NULL;

	mutex_lock(&gvt->sched_lock);

	/*
	 * no current vgpu / will be scheduled out / no workload
	 * bail out
	 */
	if (!scheduler->current_vgpu) {
		gvt_dbg_sched("ring id %d stop - no current vgpu\n", ring_id);
		goto out;
	}

	if (scheduler->need_reschedule) {
		gvt_dbg_sched("ring id %d stop - will reschedule\n", ring_id);
		goto out;
	}

	if (!scheduler->current_vgpu->active ||
	    list_empty(workload_q_head(scheduler->current_vgpu, ring_id)))
		goto out;

	/*
	 * still have current workload, maybe the workload disptacher
	 * fail to submit it for some reason, resubmit it.
	 */
	if (scheduler->current_workload[ring_id]) {
		workload = scheduler->current_workload[ring_id];
		gvt_dbg_sched("ring id %d still have current workload %p\n",
				ring_id, workload);
		goto out;
	}

	/*
	 * pick a workload as current workload
	 * once current workload is set, schedule policy routines
	 * will wait the current workload is finished when trying to
	 * schedule out a vgpu.
	 */
	scheduler->current_workload[ring_id] = container_of(
			workload_q_head(scheduler->current_vgpu, ring_id)->next,
			struct intel_vgpu_workload, list);

	workload = scheduler->current_workload[ring_id];

	gvt_dbg_sched("ring id %d pick new workload %p\n", ring_id, workload);

	atomic_inc(&workload->vgpu->submission.running_workload_num);
out:
	mutex_unlock(&gvt->sched_lock);
	return workload;
}

static void update_guest_context(struct intel_vgpu_workload *workload)
{
	struct i915_request *rq = workload->req;
	struct intel_vgpu *vgpu = workload->vgpu;
	struct intel_gvt *gvt = vgpu->gvt;
	struct drm_i915_gem_object *ctx_obj = rq->hw_context->state->obj;
	struct execlist_ring_context *shadow_ring_context;
	struct page *page;
	void *src;
	unsigned long context_gpa, context_page_num;
	int i;

	gvt_dbg_sched("ring id %d workload lrca %x\n", rq->engine->id,
		      workload->ctx_desc.lrca);

	context_page_num = rq->engine->context_size;
	context_page_num = context_page_num >> PAGE_SHIFT;

	if (IS_BROADWELL(gvt->dev_priv) && rq->engine->id == RCS)
		context_page_num = 19;

	i = 2;

	while (i < context_page_num) {
		context_gpa = intel_vgpu_gma_to_gpa(vgpu->gtt.ggtt_mm,
				(u32)((workload->ctx_desc.lrca + i) <<
					I915_GTT_PAGE_SHIFT));
		if (context_gpa == INTEL_GVT_INVALID_ADDR) {
			gvt_vgpu_err("invalid guest context descriptor\n");
			return;
		}

		page = i915_gem_object_get_page(ctx_obj, LRC_HEADER_PAGES + i);
		src = kmap(page);
		intel_gvt_hypervisor_write_gpa(vgpu, context_gpa, src,
				I915_GTT_PAGE_SIZE);
		kunmap(page);
		i++;
	}

	intel_gvt_hypervisor_write_gpa(vgpu, workload->ring_context_gpa +
		RING_CTX_OFF(ring_header.val), &workload->rb_tail, 4);

	page = i915_gem_object_get_page(ctx_obj, LRC_STATE_PN);
	shadow_ring_context = kmap(page);

#define COPY_REG(name) \
	intel_gvt_hypervisor_write_gpa(vgpu, workload->ring_context_gpa + \
		RING_CTX_OFF(name.val), &shadow_ring_context->name.val, 4)

	COPY_REG(ctx_ctrl);
	COPY_REG(ctx_timestamp);

#undef COPY_REG

	intel_gvt_hypervisor_write_gpa(vgpu,
			workload->ring_context_gpa +
			sizeof(*shadow_ring_context),
			(void *)shadow_ring_context +
			sizeof(*shadow_ring_context),
			I915_GTT_PAGE_SIZE - sizeof(*shadow_ring_context));

	kunmap(page);
}

void intel_vgpu_clean_workloads(struct intel_vgpu *vgpu,
				unsigned long engine_mask)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	struct intel_engine_cs *engine;
	struct intel_vgpu_workload *pos, *n;
	unsigned int tmp;

	/* free the unsubmited workloads in the queues. */
	for_each_engine_masked(engine, dev_priv, engine_mask, tmp) {
		list_for_each_entry_safe(pos, n,
			&s->workload_q_head[engine->id], list) {
			list_del_init(&pos->list);
			intel_vgpu_destroy_workload(pos);
		}
		clear_bit(engine->id, s->shadow_ctx_desc_updated);
	}
}

static void complete_current_workload(struct intel_gvt *gvt, int ring_id)
{
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	struct intel_vgpu_workload *workload =
		scheduler->current_workload[ring_id];
	struct intel_vgpu *vgpu = workload->vgpu;
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct i915_request *rq = workload->req;
	int event;

	mutex_lock(&vgpu->vgpu_lock);
	mutex_lock(&gvt->sched_lock);

	/* For the workload w/ request, needs to wait for the context
	 * switch to make sure request is completed.
	 * For the workload w/o request, directly complete the workload.
	 */
	if (rq) {
		wait_event(workload->shadow_ctx_status_wq,
			   !atomic_read(&workload->shadow_ctx_active));

		/* If this request caused GPU hang, req->fence.error will
		 * be set to -EIO. Use -EIO to set workload status so
		 * that when this request caused GPU hang, didn't trigger
		 * context switch interrupt to guest.
		 */
		if (likely(workload->status == -EINPROGRESS)) {
			if (workload->req->fence.error == -EIO)
				workload->status = -EIO;
			else
				workload->status = 0;
		}

		if (!workload->status && !(vgpu->resetting_eng &
					   ENGINE_MASK(ring_id))) {
			update_guest_context(workload);

			for_each_set_bit(event, workload->pending_events,
					 INTEL_GVT_EVENT_MAX)
				intel_vgpu_trigger_virtual_event(vgpu, event);
		}

		/* unpin shadow ctx as the shadow_ctx update is done */
		mutex_lock(&rq->i915->drm.struct_mutex);
		intel_context_unpin(rq->hw_context);
		mutex_unlock(&rq->i915->drm.struct_mutex);

		i915_request_put(fetch_and_zero(&workload->req));
	}

	gvt_dbg_sched("ring id %d complete workload %p status %d\n",
			ring_id, workload, workload->status);

	scheduler->current_workload[ring_id] = NULL;

	list_del_init(&workload->list);

	if (workload->status || (vgpu->resetting_eng & ENGINE_MASK(ring_id))) {
		/* if workload->status is not successful means HW GPU
		 * has occurred GPU hang or something wrong with i915/GVT,
		 * and GVT won't inject context switch interrupt to guest.
		 * So this error is a vGPU hang actually to the guest.
		 * According to this we should emunlate a vGPU hang. If
		 * there are pending workloads which are already submitted
		 * from guest, we should clean them up like HW GPU does.
		 *
		 * if it is in middle of engine resetting, the pending
		 * workloads won't be submitted to HW GPU and will be
		 * cleaned up during the resetting process later, so doing
		 * the workload clean up here doesn't have any impact.
		 **/
		intel_vgpu_clean_workloads(vgpu, ENGINE_MASK(ring_id));
	}

	workload->complete(workload);

	atomic_dec(&s->running_workload_num);
	wake_up(&scheduler->workload_complete_wq);

	if (gvt->scheduler.need_reschedule)
		intel_gvt_request_service(gvt, INTEL_GVT_REQUEST_EVENT_SCHED);

	mutex_unlock(&gvt->sched_lock);
	mutex_unlock(&vgpu->vgpu_lock);
}

struct workload_thread_param {
	struct intel_gvt *gvt;
	int ring_id;
};

static int workload_thread(void *priv)
{
	struct workload_thread_param *p = (struct workload_thread_param *)priv;
	struct intel_gvt *gvt = p->gvt;
	int ring_id = p->ring_id;
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	struct intel_vgpu_workload *workload = NULL;
	struct intel_vgpu *vgpu = NULL;
	int ret;
	bool need_force_wake = (INTEL_GEN(gvt->dev_priv) >= 9);
	DEFINE_WAIT_FUNC(wait, woken_wake_function);

	kfree(p);

	gvt_dbg_core("workload thread for ring %d started\n", ring_id);

	while (!kthread_should_stop()) {
		add_wait_queue(&scheduler->waitq[ring_id], &wait);
		do {
			workload = pick_next_workload(gvt, ring_id);
			if (workload)
				break;
			wait_woken(&wait, TASK_INTERRUPTIBLE,
				   MAX_SCHEDULE_TIMEOUT);
		} while (!kthread_should_stop());
		remove_wait_queue(&scheduler->waitq[ring_id], &wait);

		if (!workload)
			break;

		gvt_dbg_sched("ring id %d next workload %p vgpu %d\n",
				workload->ring_id, workload,
				workload->vgpu->id);

		intel_runtime_pm_get(gvt->dev_priv);

		gvt_dbg_sched("ring id %d will dispatch workload %p\n",
				workload->ring_id, workload);

		if (need_force_wake)
			intel_uncore_forcewake_get(gvt->dev_priv,
					FORCEWAKE_ALL);

		ret = dispatch_workload(workload);

		if (ret) {
			vgpu = workload->vgpu;
			gvt_vgpu_err("fail to dispatch workload, skip\n");
			goto complete;
		}

		gvt_dbg_sched("ring id %d wait workload %p\n",
				workload->ring_id, workload);
		i915_request_wait(workload->req, 0, MAX_SCHEDULE_TIMEOUT);

complete:
		gvt_dbg_sched("will complete workload %p, status: %d\n",
				workload, workload->status);

		complete_current_workload(gvt, ring_id);

		if (need_force_wake)
			intel_uncore_forcewake_put(gvt->dev_priv,
					FORCEWAKE_ALL);

		intel_runtime_pm_put_unchecked(gvt->dev_priv);
		if (ret && (vgpu_is_vm_unhealthy(ret)))
			enter_failsafe_mode(vgpu, GVT_FAILSAFE_GUEST_ERR);
	}
	return 0;
}

void intel_gvt_wait_vgpu_idle(struct intel_vgpu *vgpu)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct intel_gvt *gvt = vgpu->gvt;
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;

	if (atomic_read(&s->running_workload_num)) {
		gvt_dbg_sched("wait vgpu idle\n");

		wait_event(scheduler->workload_complete_wq,
				!atomic_read(&s->running_workload_num));
	}
}

void intel_gvt_clean_workload_scheduler(struct intel_gvt *gvt)
{
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	struct intel_engine_cs *engine;
	enum intel_engine_id i;

	gvt_dbg_core("clean workload scheduler\n");

	for_each_engine(engine, gvt->dev_priv, i) {
		atomic_notifier_chain_unregister(
					&engine->context_status_notifier,
					&gvt->shadow_ctx_notifier_block[i]);
		kthread_stop(scheduler->thread[i]);
	}
}

int intel_gvt_init_workload_scheduler(struct intel_gvt *gvt)
{
	struct intel_gvt_workload_scheduler *scheduler = &gvt->scheduler;
	struct workload_thread_param *param = NULL;
	struct intel_engine_cs *engine;
	enum intel_engine_id i;
	int ret;

	gvt_dbg_core("init workload scheduler\n");

	init_waitqueue_head(&scheduler->workload_complete_wq);

	for_each_engine(engine, gvt->dev_priv, i) {
		init_waitqueue_head(&scheduler->waitq[i]);

		param = kzalloc(sizeof(*param), GFP_KERNEL);
		if (!param) {
			ret = -ENOMEM;
			goto err;
		}

		param->gvt = gvt;
		param->ring_id = i;

		scheduler->thread[i] = kthread_run(workload_thread, param,
			"gvt workload %d", i);
		if (IS_ERR(scheduler->thread[i])) {
			gvt_err("fail to create workload thread\n");
			ret = PTR_ERR(scheduler->thread[i]);
			goto err;
		}

		gvt->shadow_ctx_notifier_block[i].notifier_call =
					shadow_context_status_change;
		atomic_notifier_chain_register(&engine->context_status_notifier,
					&gvt->shadow_ctx_notifier_block[i]);
	}
	return 0;
err:
	intel_gvt_clean_workload_scheduler(gvt);
	kfree(param);
	param = NULL;
	return ret;
}

static void
i915_context_ppgtt_root_restore(struct intel_vgpu_submission *s)
{
	struct i915_hw_ppgtt *i915_ppgtt = s->shadow_ctx->ppgtt;
	int i;

	if (i915_vm_is_48bit(&i915_ppgtt->vm))
		px_dma(&i915_ppgtt->pml4) = s->i915_context_pml4;
	else {
		for (i = 0; i < GEN8_3LVL_PDPES; i++)
			px_dma(i915_ppgtt->pdp.page_directory[i]) =
						s->i915_context_pdps[i];
	}
}

/**
 * intel_vgpu_clean_submission - free submission-related resource for vGPU
 * @vgpu: a vGPU
 *
 * This function is called when a vGPU is being destroyed.
 *
 */
void intel_vgpu_clean_submission(struct intel_vgpu *vgpu)
{
	struct intel_vgpu_submission *s = &vgpu->submission;

	intel_vgpu_select_submission_ops(vgpu, ALL_ENGINES, 0);
	i915_context_ppgtt_root_restore(s);
	i915_gem_context_put(s->shadow_ctx);
	kmem_cache_destroy(s->workloads);
}


/**
 * intel_vgpu_reset_submission - reset submission-related resource for vGPU
 * @vgpu: a vGPU
 * @engine_mask: engines expected to be reset
 *
 * This function is called when a vGPU is being destroyed.
 *
 */
void intel_vgpu_reset_submission(struct intel_vgpu *vgpu,
		unsigned long engine_mask)
{
	struct intel_vgpu_submission *s = &vgpu->submission;

	if (!s->active)
		return;

	intel_vgpu_clean_workloads(vgpu, engine_mask);
	s->ops->reset(vgpu, engine_mask);
}

static void
i915_context_ppgtt_root_save(struct intel_vgpu_submission *s)
{
	struct i915_hw_ppgtt *i915_ppgtt = s->shadow_ctx->ppgtt;
	int i;

	if (i915_vm_is_48bit(&i915_ppgtt->vm))
		s->i915_context_pml4 = px_dma(&i915_ppgtt->pml4);
	else {
		for (i = 0; i < GEN8_3LVL_PDPES; i++)
			s->i915_context_pdps[i] =
				px_dma(i915_ppgtt->pdp.page_directory[i]);
	}
}

/**
 * intel_vgpu_setup_submission - setup submission-related resource for vGPU
 * @vgpu: a vGPU
 *
 * This function is called when a vGPU is being created.
 *
 * Returns:
 * Zero on success, negative error code if failed.
 *
 */
int intel_vgpu_setup_submission(struct intel_vgpu *vgpu)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	enum intel_engine_id i;
	struct intel_engine_cs *engine;
	int ret;

	s->shadow_ctx = i915_gem_context_create_gvt(
			&vgpu->gvt->dev_priv->drm);
	if (IS_ERR(s->shadow_ctx))
		return PTR_ERR(s->shadow_ctx);

	i915_context_ppgtt_root_save(s);

	bitmap_zero(s->shadow_ctx_desc_updated, I915_NUM_ENGINES);

	s->workloads = kmem_cache_create_usercopy("gvt-g_vgpu_workload",
						  sizeof(struct intel_vgpu_workload), 0,
						  SLAB_HWCACHE_ALIGN,
						  offsetof(struct intel_vgpu_workload, rb_tail),
						  sizeof_field(struct intel_vgpu_workload, rb_tail),
						  NULL);

	if (!s->workloads) {
		ret = -ENOMEM;
		goto out_shadow_ctx;
	}

	for_each_engine(engine, vgpu->gvt->dev_priv, i)
		INIT_LIST_HEAD(&s->workload_q_head[i]);

	atomic_set(&s->running_workload_num, 0);
	bitmap_zero(s->tlb_handle_pending, I915_NUM_ENGINES);

	return 0;

out_shadow_ctx:
	i915_gem_context_put(s->shadow_ctx);
	return ret;
}

/**
 * intel_vgpu_select_submission_ops - select virtual submission interface
 * @vgpu: a vGPU
 * @engine_mask: either ALL_ENGINES or target engine mask
 * @interface: expected vGPU virtual submission interface
 *
 * This function is called when guest configures submission interface.
 *
 * Returns:
 * Zero on success, negative error code if failed.
 *
 */
int intel_vgpu_select_submission_ops(struct intel_vgpu *vgpu,
				     unsigned long engine_mask,
				     unsigned int interface)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	const struct intel_vgpu_submission_ops *ops[] = {
		[INTEL_VGPU_EXECLIST_SUBMISSION] =
			&intel_vgpu_execlist_submission_ops,
	};
	int ret;

	if (WARN_ON(interface >= ARRAY_SIZE(ops)))
		return -EINVAL;

	if (WARN_ON(interface == 0 && engine_mask != ALL_ENGINES))
		return -EINVAL;

	if (s->active)
		s->ops->clean(vgpu, engine_mask);

	if (interface == 0) {
		s->ops = NULL;
		s->virtual_submission_interface = 0;
		s->active = false;
		gvt_dbg_core("vgpu%d: remove submission ops\n", vgpu->id);
		return 0;
	}

	ret = ops[interface]->init(vgpu, engine_mask);
	if (ret)
		return ret;

	s->ops = ops[interface];
	s->virtual_submission_interface = interface;
	s->active = true;

	gvt_dbg_core("vgpu%d: activate ops [ %s ]\n",
			vgpu->id, s->ops->name);

	return 0;
}

/**
 * intel_vgpu_destroy_workload - destroy a vGPU workload
 * @workload: workload to destroy
 *
 * This function is called when destroy a vGPU workload.
 *
 */
void intel_vgpu_destroy_workload(struct intel_vgpu_workload *workload)
{
	struct intel_vgpu_submission *s = &workload->vgpu->submission;

	release_shadow_batch_buffer(workload);
	release_shadow_wa_ctx(&workload->wa_ctx);

	if (workload->shadow_mm)
		intel_vgpu_mm_put(workload->shadow_mm);

	kmem_cache_free(s->workloads, workload);
}

static struct intel_vgpu_workload *
alloc_workload(struct intel_vgpu *vgpu)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct intel_vgpu_workload *workload;

	workload = kmem_cache_zalloc(s->workloads, GFP_KERNEL);
	if (!workload)
		return ERR_PTR(-ENOMEM);

	INIT_LIST_HEAD(&workload->list);
	INIT_LIST_HEAD(&workload->shadow_bb);

	init_waitqueue_head(&workload->shadow_ctx_status_wq);
	atomic_set(&workload->shadow_ctx_active, 0);

	workload->status = -EINPROGRESS;
	workload->vgpu = vgpu;

	return workload;
}

#define RING_CTX_OFF(x) \
	offsetof(struct execlist_ring_context, x)

static void read_guest_pdps(struct intel_vgpu *vgpu,
		u64 ring_context_gpa, u32 pdp[8])
{
	u64 gpa;
	int i;

	gpa = ring_context_gpa + RING_CTX_OFF(pdps[0].val);

	for (i = 0; i < 8; i++)
		intel_gvt_hypervisor_read_gpa(vgpu,
				gpa + i * 8, &pdp[7 - i], 4);
}

static int prepare_mm(struct intel_vgpu_workload *workload)
{
	struct execlist_ctx_descriptor_format *desc = &workload->ctx_desc;
	struct intel_vgpu_mm *mm;
	struct intel_vgpu *vgpu = workload->vgpu;
	intel_gvt_gtt_type_t root_entry_type;
	u64 pdps[GVT_RING_CTX_NR_PDPS];

	switch (desc->addressing_mode) {
	case 1: /* legacy 32-bit */
		root_entry_type = GTT_TYPE_PPGTT_ROOT_L3_ENTRY;
		break;
	case 3: /* legacy 64-bit */
		root_entry_type = GTT_TYPE_PPGTT_ROOT_L4_ENTRY;
		break;
	default:
		gvt_vgpu_err("Advanced Context mode(SVM) is not supported!\n");
		return -EINVAL;
	}

	read_guest_pdps(workload->vgpu, workload->ring_context_gpa, (void *)pdps);

	mm = intel_vgpu_get_ppgtt_mm(workload->vgpu, root_entry_type, pdps);
	if (IS_ERR(mm))
		return PTR_ERR(mm);

	workload->shadow_mm = mm;
	return 0;
}

#define same_context(a, b) (((a)->context_id == (b)->context_id) && \
		((a)->lrca == (b)->lrca))

#define get_last_workload(q) \
	(list_empty(q) ? NULL : container_of(q->prev, \
	struct intel_vgpu_workload, list))
/**
 * intel_vgpu_create_workload - create a vGPU workload
 * @vgpu: a vGPU
 * @ring_id: ring index
 * @desc: a guest context descriptor
 *
 * This function is called when creating a vGPU workload.
 *
 * Returns:
 * struct intel_vgpu_workload * on success, negative error code in
 * pointer if failed.
 *
 */
struct intel_vgpu_workload *
intel_vgpu_create_workload(struct intel_vgpu *vgpu, int ring_id,
			   struct execlist_ctx_descriptor_format *desc)
{
	struct intel_vgpu_submission *s = &vgpu->submission;
	struct list_head *q = workload_q_head(vgpu, ring_id);
	struct intel_vgpu_workload *last_workload = get_last_workload(q);
	struct intel_vgpu_workload *workload = NULL;
	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
	u64 ring_context_gpa;
	u32 head, tail, start, ctl, ctx_ctl, per_ctx, indirect_ctx;
	int ret;

	ring_context_gpa = intel_vgpu_gma_to_gpa(vgpu->gtt.ggtt_mm,
			(u32)((desc->lrca + 1) << I915_GTT_PAGE_SHIFT));
	if (ring_context_gpa == INTEL_GVT_INVALID_ADDR) {
		gvt_vgpu_err("invalid guest context LRCA: %x\n", desc->lrca);
		return ERR_PTR(-EINVAL);
	}

	intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(ring_header.val), &head, 4);

	intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(ring_tail.val), &tail, 4);

	head &= RB_HEAD_OFF_MASK;
	tail &= RB_TAIL_OFF_MASK;

	if (last_workload && same_context(&last_workload->ctx_desc, desc)) {
		gvt_dbg_el("ring id %d cur workload == last\n", ring_id);
		gvt_dbg_el("ctx head %x real head %lx\n", head,
				last_workload->rb_tail);
		/*
		 * cannot use guest context head pointer here,
		 * as it might not be updated at this time
		 */
		head = last_workload->rb_tail;
	}

	gvt_dbg_el("ring id %d begin a new workload\n", ring_id);

	/* record some ring buffer register values for scan and shadow */
	intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(rb_start.val), &start, 4);
	intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(rb_ctrl.val), &ctl, 4);
	intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(ctx_ctrl.val), &ctx_ctl, 4);

	workload = alloc_workload(vgpu);
	if (IS_ERR(workload))
		return workload;

	workload->ring_id = ring_id;
	workload->ctx_desc = *desc;
	workload->ring_context_gpa = ring_context_gpa;
	workload->rb_head = head;
	workload->rb_tail = tail;
	workload->rb_start = start;
	workload->rb_ctl = ctl;

	if (ring_id == RCS) {
		intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(bb_per_ctx_ptr.val), &per_ctx, 4);
		intel_gvt_hypervisor_read_gpa(vgpu, ring_context_gpa +
			RING_CTX_OFF(rcs_indirect_ctx.val), &indirect_ctx, 4);

		workload->wa_ctx.indirect_ctx.guest_gma =
			indirect_ctx & INDIRECT_CTX_ADDR_MASK;
		workload->wa_ctx.indirect_ctx.size =
			(indirect_ctx & INDIRECT_CTX_SIZE_MASK) *
			CACHELINE_BYTES;
		workload->wa_ctx.per_ctx.guest_gma =
			per_ctx & PER_CTX_ADDR_MASK;
		workload->wa_ctx.per_ctx.valid = per_ctx & 1;
	}

	gvt_dbg_el("workload %p ring id %d head %x tail %x start %x ctl %x\n",
			workload, ring_id, head, tail, start, ctl);

	ret = prepare_mm(workload);
	if (ret) {
		kmem_cache_free(s->workloads, workload);
		return ERR_PTR(ret);
	}

	/* Only scan and shadow the first workload in the queue
	 * as there is only one pre-allocated buf-obj for shadow.
	 */
	if (list_empty(workload_q_head(vgpu, ring_id))) {
		intel_runtime_pm_get(dev_priv);
		mutex_lock(&dev_priv->drm.struct_mutex);
		ret = intel_gvt_scan_and_shadow_workload(workload);
		mutex_unlock(&dev_priv->drm.struct_mutex);
		intel_runtime_pm_put_unchecked(dev_priv);
	}

	if (ret && (vgpu_is_vm_unhealthy(ret))) {
		enter_failsafe_mode(vgpu, GVT_FAILSAFE_GUEST_ERR);
		intel_vgpu_destroy_workload(workload);
		return ERR_PTR(ret);
	}

	return workload;
}

/**
 * intel_vgpu_queue_workload - Qeue a vGPU workload
 * @workload: the workload to queue in
 */
void intel_vgpu_queue_workload(struct intel_vgpu_workload *workload)
{
	list_add_tail(&workload->list,
		workload_q_head(workload->vgpu, workload->ring_id));
	intel_gvt_kick_schedule(workload->vgpu->gvt);
	wake_up(&workload->vgpu->gvt->scheduler.waitq[workload->ring_id]);
}