drm/i915/gvt: do not let TRTTE and 0x4dfc write passthrough to hardware

the vGPU write on TRTTE and 0x4dfc is now write to vreg first. their
values all be restored hardware when context switching.

Fixes: e39c5add ("drm/i915/gvt: vGPU MMIO virtualization")
Acked-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NYan Zhao <yan.y.zhao@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -1364,7 +1364,6 @@ static int dma_ctrl_write(struct intel_vgpu *vgpu, unsigned int offset,
 static int gen9_trtte_write(struct intel_vgpu *vgpu, unsigned int offset,
 		void *p_data, unsigned int bytes)
 {
-	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
 	u32 trtte = *(u32 *)p_data;
 
 	if ((trtte & 1) && (trtte & (1 << 1)) == 0) {
@@ -1373,11 +1372,6 @@ static int gen9_trtte_write(struct intel_vgpu *vgpu, unsigned int offset,
 		return -EINVAL;
 	}
 	write_vreg(vgpu, offset, p_data, bytes);
-	/* TRTTE is not per-context */
-
-	mmio_hw_access_pre(dev_priv);
-	I915_WRITE(_MMIO(offset), vgpu_vreg(vgpu, offset));
-	mmio_hw_access_post(dev_priv);
 
 	return 0;
 }
@@ -1385,15 +1379,6 @@ static int gen9_trtte_write(struct intel_vgpu *vgpu, unsigned int offset,
 static int gen9_trtt_chicken_write(struct intel_vgpu *vgpu, unsigned int offset,
 		void *p_data, unsigned int bytes)
 {
-	struct drm_i915_private *dev_priv = vgpu->gvt->dev_priv;
-	u32 val = *(u32 *)p_data;
-
-	if (val & 1) {
-		/* unblock hw logic */
-		mmio_hw_access_pre(dev_priv);
-		I915_WRITE(_MMIO(offset), val);
-		mmio_hw_access_post(dev_priv);
-	}
 	write_vreg(vgpu, offset, p_data, bytes);
 	return 0;
 }