drm/i915/gvt: Refine virtual reset function

during the emulation of virtual reset:
1. only reset the engine related mmio ending with MMIO
   offset Master_IRQ, not include display stuff.

2. fences are not required to set default
   value as well to prevent screen flicking.

this will fix the issue of Guest screen hang while running
Force tdr in Linux guest.

v2:
- only reset the engine related mmio. (Zhenyu & Zhiyuan)
v3:
- IMR/Ring mode registers are not save/restored. (Changbin)
v4:
- redefine the MMIO reset offset for easy understanding. (Zhenyu)
- pvinfo can be reset. (Zhenyu)
v5:
- add more comments for mmio reset. (Zhenyu)

Cc: Changbin Du <changbin.du@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Lv zhiyuan <zhiyuan.lv@intel.com>
Cc: Zhang Yulei <yulei.zhang@intel.com>
Signed-off-by: fred gao <fred.gao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/gvt/vgpu.c b/drivers/gpu/drm/i915/gvt/vgpu.c
index 6e3cbd8caec2..90c14e6e3ea0 100644
--- a/drivers/gpu/drm/i915/gvt/vgpu.c
+++ b/drivers/gpu/drm/i915/gvt/vgpu.c
@@ -501,9 +501,14 @@ void intel_gvt_reset_vgpu_locked(struct intel_vgpu *vgpu, bool dmlr,
 
 	/* full GPU reset or device model level reset */
 	if (engine_mask == ALL_ENGINES || dmlr) {
+
 		intel_vgpu_reset_gtt(vgpu, dmlr);
-		intel_vgpu_reset_resource(vgpu);
-		intel_vgpu_reset_mmio(vgpu);
+
+		/*fence will not be reset during virtual reset */
+		if (dmlr)
+			intel_vgpu_reset_resource(vgpu);
+
+		intel_vgpu_reset_mmio(vgpu, dmlr);
 		populate_pvinfo_page(vgpu);
 		intel_vgpu_reset_display(vgpu);