drm/i915/gvt: implement scratch page table tree for shadow PPGTT

All the unused entries in the page table tree(PML4E->PDPE->PDE->PTE)
should point to scratch page table/scratch page to avoid page walk error
due to the page prefetching.
When removing an entry in shadow PPGTT,  it need map to scratch page
also, the older implementation use single scratch page to assign to all
level entries, it doesn't align the page walk behavior when removed
entry is in PML, PDP, PD.  To avoid potential page walk error this patch
implement a scratch page tree to replace the single scratch page.

v2: more details in commit message address Kevin's comments.

Signed-off-by: Ping Gao <ping.a.gao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 38 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/gvt/gtt.h b/drivers/gpu/drm/i915/gvt/gtt.h
index e4dcde78f3f9..d250013bc37b 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.h
+++ b/drivers/gpu/drm/i915/gvt/gtt.h
@@ -88,6 +88,36 @@ enum {
 	INTEL_GVT_MM_PPGTT,
 };
 
+typedef enum {
+	GTT_TYPE_INVALID = -1,
+
+	GTT_TYPE_GGTT_PTE,
+
+	GTT_TYPE_PPGTT_PTE_4K_ENTRY,
+	GTT_TYPE_PPGTT_PTE_2M_ENTRY,
+	GTT_TYPE_PPGTT_PTE_1G_ENTRY,
+
+	GTT_TYPE_PPGTT_PTE_ENTRY,
+
+	GTT_TYPE_PPGTT_PDE_ENTRY,
+	GTT_TYPE_PPGTT_PDP_ENTRY,
+	GTT_TYPE_PPGTT_PML4_ENTRY,
+
+	GTT_TYPE_PPGTT_ROOT_ENTRY,
+
+	GTT_TYPE_PPGTT_ROOT_L3_ENTRY,
+	GTT_TYPE_PPGTT_ROOT_L4_ENTRY,
+
+	GTT_TYPE_PPGTT_ENTRY,
+
+	GTT_TYPE_PPGTT_PTE_PT,
+	GTT_TYPE_PPGTT_PDE_PT,
+	GTT_TYPE_PPGTT_PDP_PT,
+	GTT_TYPE_PPGTT_PML4_PT,
+
+	GTT_TYPE_MAX,
+} intel_gvt_gtt_type_t;
+
 struct intel_vgpu_mm {
 	int type;
 	bool initialized;
@@ -151,6 +181,12 @@ extern void intel_vgpu_destroy_mm(struct kref *mm_ref);
 
 struct intel_vgpu_guest_page;
 
+struct intel_vgpu_scratch_pt {
+	struct page *page;
+	unsigned long page_mfn;
+};
+
+
 struct intel_vgpu_gtt {
 	struct intel_vgpu_mm *ggtt_mm;
 	unsigned long active_ppgtt_mm_bitmap;
@@ -160,8 +196,8 @@ struct intel_vgpu_gtt {
 	atomic_t n_write_protected_guest_page;
 	struct list_head oos_page_list_head;
 	struct list_head post_shadow_list_head;
-	struct page *scratch_page;
-	unsigned long scratch_page_mfn;
+	struct intel_vgpu_scratch_pt scratch_pt[GTT_TYPE_MAX];
+
 };
 
 extern int intel_vgpu_init_gtt(struct intel_vgpu *vgpu);