drm/i915/gvt: Refine broken PPGTT scratch

Refine previously broken PPGTT scratch. Scratch PTE was no correctly
handled and also the handling of scratch entries in page table walk was
not well organized, which brings gaps of introducing lazy shadow.
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>

drivers/gpu/drm/i915/gvt/gtt.c

@@ -841,20 +841,51 @@ static struct intel_vgpu_ppgtt_spt *ppgtt_find_shadow_page(
 	return NULL;
 }
 
+static bool ppgtt_is_scratch_entry(struct intel_vgpu *vgpu,
+		struct intel_gvt_gtt_entry *e)
+{
+	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
+	int pt_type = get_pt_type(e->type);
+
+	if (pt_type == GTT_TYPE_INVALID)
+		return false;
+
+	if (ops->get_pfn(e) == vgpu->gtt.ppgtt_scratch_page[pt_type].mfn)
+		return true;
+
+	return false;
+}
+
+static void ppgtt_get_scratch_entry(struct intel_vgpu *vgpu, int type,
+		struct intel_gvt_gtt_entry *e)
+{
+	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
+	struct intel_vgpu_shadow_page *scratch_page;
+	int pt_type = get_pt_type(type);
+
+	if (WARN_ON(pt_type == GTT_TYPE_INVALID))
+		return;
+
+	scratch_page = &vgpu->gtt.ppgtt_scratch_page[pt_type];
+
+	e->type = get_entry_type(type);
+	ops->get_entry(scratch_page->vaddr, e, 0, false, 0, vgpu);
+}
+
 #define pt_entry_size_shift(spt) \
 	((spt)->vgpu->gvt->device_info.gtt_entry_size_shift)
 
 #define pt_entries(spt) \
 	(I915_GTT_PAGE_SIZE >> pt_entry_size_shift(spt))
 
-#define for_each_present_guest_entry(spt, e, i) \
+#define for_each_guest_entry(spt, e, i) \
 	for (i = 0; i < pt_entries(spt); i++) \
-		if (!ppgtt_get_guest_entry(spt, e, i) && \
-		    spt->vgpu->gvt->gtt.pte_ops->test_present(e))
+		if (!ppgtt_get_guest_entry(spt, e, i))
 
 #define for_each_present_shadow_entry(spt, e, i) \
 	for (i = 0; i < pt_entries(spt); i++) \
 		if (!ppgtt_get_shadow_entry(spt, e, i) && \
+		    !ppgtt_is_scratch_entry(spt->vgpu, e) && \
 		    spt->vgpu->gvt->gtt.pte_ops->test_present(e))
 
 static void ppgtt_get_shadow_page(struct intel_vgpu_ppgtt_spt *spt)
@@ -873,18 +904,13 @@ static int ppgtt_invalidate_shadow_page_by_shadow_entry(struct intel_vgpu *vgpu,
 {
 	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
 	struct intel_vgpu_ppgtt_spt *s;
-	intel_gvt_gtt_type_t cur_pt_type;
 
 	if (WARN_ON(!gtt_type_is_pt(get_next_pt_type(e->type))))
 		return -EINVAL;
 
-	if (e->type != GTT_TYPE_PPGTT_ROOT_L3_ENTRY
-		&& e->type != GTT_TYPE_PPGTT_ROOT_L4_ENTRY) {
-		cur_pt_type = get_next_pt_type(e->type) + 1;
-		if (ops->get_pfn(e) ==
-			vgpu->gtt.scratch_pt[cur_pt_type].page_mfn)
-			return 0;
-	}
+	if (WARN_ON(ppgtt_is_scratch_entry(vgpu, e)))
+		return -EINVAL;
+
 	s = ppgtt_find_shadow_page(vgpu, ops->get_pfn(e));
 	if (!s) {
 		gvt_vgpu_err("fail to find shadow page: mfn: 0x%lx\n",
@@ -997,6 +1023,7 @@ static inline void ppgtt_generate_shadow_entry(struct intel_gvt_gtt_entry *se,
 static int ppgtt_populate_shadow_page(struct intel_vgpu_ppgtt_spt *spt)
 {
 	struct intel_vgpu *vgpu = spt->vgpu;
+	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
 	struct intel_vgpu_ppgtt_spt *s;
 	struct intel_gvt_gtt_entry se, ge;
 	unsigned long i;
@@ -1006,22 +1033,34 @@ static int ppgtt_populate_shadow_page(struct intel_vgpu_ppgtt_spt *spt)
 			spt->guest_page.track.gfn, spt->shadow_page.type);
 
 	if (gtt_type_is_pte_pt(spt->shadow_page.type)) {
-		for_each_present_guest_entry(spt, &ge, i) {
-			ret = gtt_entry_p2m(vgpu, &ge, &se);
-			if (ret)
-				goto fail;
+		for_each_guest_entry(spt, &ge, i) {
+			if (ops->test_present(&ge)) {
+				ret = gtt_entry_p2m(vgpu, &ge, &se);
+				if (ret)
+					goto fail;
+			} else {
+				ppgtt_get_scratch_entry(vgpu,
+						spt->shadow_page.type, &se);
+			}
 			ppgtt_set_shadow_entry(spt, &se, i);
 		}
 		return 0;
 	}
 
-	for_each_present_guest_entry(spt, &ge, i) {
+	for_each_guest_entry(spt, &ge, i) {
 		if (!gtt_type_is_pt(get_next_pt_type(ge.type))) {
 			gvt_vgpu_err("GVT doesn't support pse bit now\n");
 			ret = -EINVAL;
 			goto fail;
 		}
 
+		if (!ops->test_present(&ge)) {
+			ppgtt_get_scratch_entry(vgpu, spt->shadow_page.type,
+					&se);
+			ppgtt_set_shadow_entry(spt, &se, i);
+			continue;
+		}
+
 		s = ppgtt_populate_shadow_page_by_guest_entry(vgpu, &ge);
 		if (IS_ERR(s)) {
 			ret = PTR_ERR(s);
@@ -1053,7 +1092,7 @@ static int ppgtt_handle_guest_entry_removal(struct intel_vgpu_guest_page *gpt,
 	if (!ops->test_present(se))
 		return 0;
 
-	if (ops->get_pfn(se) == vgpu->gtt.scratch_pt[sp->type].page_mfn)
+	if (ppgtt_is_scratch_entry(vgpu, se))
 		return 0;
 
 	if (gtt_type_is_pt(get_next_pt_type(se->type))) {
@@ -1292,7 +1331,6 @@ static int ppgtt_handle_guest_write_page_table(
 {
 	struct intel_vgpu_ppgtt_spt *spt = guest_page_to_ppgtt_spt(gpt);
 	struct intel_vgpu *vgpu = spt->vgpu;
-	int type = spt->shadow_page.type;
 	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
 	struct intel_gvt_gtt_entry se;
 
@@ -1319,7 +1357,7 @@ static int ppgtt_handle_guest_write_page_table(
 		goto fail;
 
 	if (!new_present) {
-		ops->set_pfn(&se, vgpu->gtt.scratch_pt[type].page_mfn);
+		ppgtt_get_scratch_entry(vgpu, spt->shadow_page.type, &se);
 		ppgtt_set_shadow_entry(spt, &se, index);
 	}
 
@@ -1968,106 +2006,85 @@ int intel_vgpu_emulate_gtt_mmio_write(struct intel_vgpu *vgpu, unsigned int off,
 	return ret;
 }
 
-static int alloc_scratch_pages(struct intel_vgpu *vgpu,
+static void ppgtt_destroy_scratch(struct intel_vgpu *vgpu)
+{
+	struct intel_vgpu_shadow_page *scratch_page;
+	int i;
+
+	for (i = GTT_TYPE_PPGTT_PTE_PT; i < GTT_TYPE_MAX; i++) {
+		scratch_page = &vgpu->gtt.ppgtt_scratch_page[i];
+		if (scratch_page->page != NULL) {
+			clean_shadow_page(vgpu, scratch_page);
+			__free_page(scratch_page->page);
+		}
+	}
+}
+
+static int setup_ppgtt_scratch_page(struct intel_vgpu *vgpu,
 		intel_gvt_gtt_type_t type)
 {
+	struct intel_gvt *gvt = vgpu->gvt;
+	struct intel_gvt_device_info *info = &gvt->device_info;
+	int num_entries = I915_GTT_PAGE_SIZE >> info->gtt_entry_size_shift;
 	struct intel_vgpu_gtt *gtt = &vgpu->gtt;
 	struct intel_gvt_gtt_pte_ops *ops = vgpu->gvt->gtt.pte_ops;
-	int page_entry_num = I915_GTT_PAGE_SIZE >>
-				vgpu->gvt->device_info.gtt_entry_size_shift;
-	void *scratch_pt;
-	int i;
-	struct device *dev = &vgpu->gvt->dev_priv->drm.pdev->dev;
-	dma_addr_t daddr;
+	struct intel_vgpu_shadow_page *scratch_page;
+	struct intel_gvt_gtt_entry e;
+	intel_gvt_gtt_type_t next_pt_type;
+	int ret, i;
 
 	if (WARN_ON(type < GTT_TYPE_PPGTT_PTE_PT || type >= GTT_TYPE_MAX))
 		return -EINVAL;
 
-	scratch_pt = (void *)get_zeroed_page(GFP_KERNEL);
-	if (!scratch_pt) {
+	scratch_page = &gtt->ppgtt_scratch_page[type];
+
+	scratch_page->page = alloc_page(GFP_KERNEL);
+	if (!scratch_page) {
 		gvt_vgpu_err("fail to allocate scratch page\n");
 		return -ENOMEM;
 	}
 
-	daddr = dma_map_page(dev, virt_to_page(scratch_pt), 0,
-			4096, PCI_DMA_BIDIRECTIONAL);
-	if (dma_mapping_error(dev, daddr)) {
-		gvt_vgpu_err("fail to dmamap scratch_pt\n");
-		__free_page(virt_to_page(scratch_pt));
+	ret = init_shadow_page(vgpu, scratch_page, type, false);
+	if (ret) {
+		gvt_vgpu_err("fail to allocate scratch page\n");
+		__free_page(scratch_page->page);
 		return -ENOMEM;
 	}
-	gtt->scratch_pt[type].page_mfn =
-		(unsigned long)(daddr >> I915_GTT_PAGE_SHIFT);
-	gtt->scratch_pt[type].page = virt_to_page(scratch_pt);
-	gvt_dbg_mm("vgpu%d create scratch_pt: type %d mfn=0x%lx\n",
-			vgpu->id, type, gtt->scratch_pt[type].page_mfn);
-
-	/* Build the tree by full filled the scratch pt with the entries which
-	 * point to the next level scratch pt or scratch page. The
-	 * scratch_pt[type] indicate the scratch pt/scratch page used by the
-	 * 'type' pt.
-	 * e.g. scratch_pt[GTT_TYPE_PPGTT_PDE_PT] is used by
-	 * GTT_TYPE_PPGTT_PDE_PT level pt, that means this scratch_pt it self
-	 * is GTT_TYPE_PPGTT_PTE_PT, and full filled by scratch page mfn.
-	 */
-	if (type > GTT_TYPE_PPGTT_PTE_PT && type < GTT_TYPE_MAX) {
-		struct intel_gvt_gtt_entry se;
-
-		memset(&se, 0, sizeof(struct intel_gvt_gtt_entry));
-		se.type = get_entry_type(type - 1);
-		ops->set_pfn(&se, gtt->scratch_pt[type - 1].page_mfn);
-
-		/* The entry parameters like present/writeable/cache type
-		 * set to the same as i915's scratch page tree.
-		 */
-		se.val64 |= _PAGE_PRESENT | _PAGE_RW;
-		if (type == GTT_TYPE_PPGTT_PDE_PT)
-			se.val64 |= PPAT_CACHED;
-
-		for (i = 0; i < page_entry_num; i++)
-			ops->set_entry(scratch_pt, &se, i, false, 0, vgpu);
-	}
 
-	return 0;
-}
-
-static int release_scratch_page_tree(struct intel_vgpu *vgpu)
-{
-	int i;
-	struct device *dev = &vgpu->gvt->dev_priv->drm.pdev->dev;
-	dma_addr_t daddr;
+	memset(&e, 0, sizeof(e));
 
-	for (i = GTT_TYPE_PPGTT_PTE_PT; i < GTT_TYPE_MAX; i++) {
-		if (vgpu->gtt.scratch_pt[i].page != NULL) {
-			daddr = (dma_addr_t)(vgpu->gtt.scratch_pt[i].page_mfn <<
-					I915_GTT_PAGE_SHIFT);
-			dma_unmap_page(dev, daddr, 4096, PCI_DMA_BIDIRECTIONAL);
-			__free_page(vgpu->gtt.scratch_pt[i].page);
-			vgpu->gtt.scratch_pt[i].page = NULL;
-			vgpu->gtt.scratch_pt[i].page_mfn = 0;
-		}
+	if (type == GTT_TYPE_PPGTT_PTE_PT) {
+		e.type = GTT_TYPE_PPGTT_PTE_4K_ENTRY;
+		ops->set_pfn(&e, gvt->gtt.scratch_mfn);
+	} else {
+		next_pt_type = get_next_pt_type(type);
+		e.type = get_entry_type(type);
+		ops->set_pfn(&e, gtt->ppgtt_scratch_page[next_pt_type].mfn);
 	}
 
+	ops->set_present(&e);
+
+	for (i = 0; i < num_entries; i++)
+		ops->set_entry(scratch_page->vaddr, &e, i, false, 0, vgpu);
+
 	return 0;
 }
 
-static int create_scratch_page_tree(struct intel_vgpu *vgpu)
+static int ppgtt_create_scratch(struct intel_vgpu *vgpu)
 {
 	int i, ret;
 
 	for (i = GTT_TYPE_PPGTT_PTE_PT; i < GTT_TYPE_MAX; i++) {
-		ret = alloc_scratch_pages(vgpu, i);
+		ret = setup_ppgtt_scratch_page(vgpu, i);
 		if (ret)
 			goto err;
 	}
-
 	return 0;
-
 err:
-	release_scratch_page_tree(vgpu);
+	ppgtt_destroy_scratch(vgpu);
 	return ret;
 }
-
+ 
 /**
  * intel_vgpu_init_gtt - initialize per-vGPU graphics memory virulization
  * @vgpu: a vGPU
@@ -2100,8 +2117,7 @@ int intel_vgpu_init_gtt(struct intel_vgpu *vgpu)
 	}
 
 	gtt->ggtt_mm = ggtt_mm;
-
-	return create_scratch_page_tree(vgpu);
+	return ppgtt_create_scratch(vgpu);
 }
 
 static void intel_vgpu_free_mm(struct intel_vgpu *vgpu, int type)
@@ -2133,7 +2149,7 @@ static void intel_vgpu_free_mm(struct intel_vgpu *vgpu, int type)
 void intel_vgpu_clean_gtt(struct intel_vgpu *vgpu)
 {
 	ppgtt_free_all_shadow_page(vgpu);
-	release_scratch_page_tree(vgpu);
+	ppgtt_destroy_scratch(vgpu);
 
 	intel_vgpu_free_mm(vgpu, INTEL_GVT_MM_PPGTT);
 	intel_vgpu_free_mm(vgpu, INTEL_GVT_MM_GGTT);

drivers/gpu/drm/i915/gvt/gtt.h

@@ -188,9 +188,12 @@ extern void intel_vgpu_destroy_mm(struct kref *mm_ref);
 
 struct intel_vgpu_guest_page;
 
-struct intel_vgpu_scratch_pt {
+struct intel_vgpu_shadow_page {
+	void *vaddr;
 	struct page *page;
-	unsigned long page_mfn;
+	int type;
+	struct hlist_node node;
+	unsigned long mfn;
 };
 
 struct intel_vgpu_gtt {
@@ -202,7 +205,7 @@ struct intel_vgpu_gtt {
 	atomic_t n_tracked_guest_page;
 	struct list_head oos_page_list_head;
 	struct list_head post_shadow_list_head;
-	struct intel_vgpu_scratch_pt scratch_pt[GTT_TYPE_MAX];
+	struct intel_vgpu_shadow_page ppgtt_scratch_page[GTT_TYPE_MAX];
 };
 
 extern int intel_vgpu_init_gtt(struct intel_vgpu *vgpu);
@@ -218,14 +221,6 @@ extern struct intel_vgpu_mm *intel_gvt_find_ppgtt_mm(struct intel_vgpu *vgpu,
 
 struct intel_vgpu_oos_page;
 
-struct intel_vgpu_shadow_page {
-	void *vaddr;
-	struct page *page;
-	int type;
-	struct hlist_node node;
-	unsigned long mfn;
-};
-
 struct intel_vgpu_page_track {
 	struct hlist_node node;
 	bool tracked;