[PATCH] drm/i915/gvt: set shadow entry to scratch page while p2m failed

[Xiaoguang Chen]

Sometimes guest driver will only update partial of the GGTT entry then
access it. In this situation a failure will happen while translating
the gpa to hpa.
Now in this situation we let the corresponding shadow entry pointing
to a scratch page.

Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
Signed-off-by: Xiaoguang Chen <xiaoguang.chen at intel.com>
---
 drivers/gpu/drm/i915/gvt/gtt.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c
index da73127..96aa30c 100644
--- a/drivers/gpu/drm/i915/gvt/gtt.c
+++ b/drivers/gpu/drm/i915/gvt/gtt.c
@@ -1837,11 +1837,17 @@ static int emulate_gtt_mmio_write(struct intel_vgpu *vgpu, unsigned int off,
 		ret = gtt_entry_p2m(vgpu, &e, &m);
 		if (ret) {
 			gvt_vgpu_err("fail to translate guest gtt entry\n");
-			return ret;
+			/* guest driver may read/write the entry when partial
+			 * update the entry in this situation p2m will fail
+			 * settting the shadow entry to point to a scratch page
+			 */
+			ops->set_pfn(&m,
+			vgpu->gtt.scratch_pt[GTT_TYPE_GGTT_PTE].page_mfn);
 		}
 	} else {
 		m = e;
-		m.val64 = 0;
+		ops->set_pfn(&m,
+		vgpu->gtt.scratch_pt[GTT_TYPE_GGTT_PTE].page_mfn);
 	}
 
 	ggtt_set_shadow_entry(ggtt_mm, &m, g_gtt_index);
-- 
2.7.4