drm/i915: Add new vGPU cap info bit VGT_CAPS_HUGE_GTT

This adds a new vGPU cap info bit VGT_CAPS_HUGE_GTT, which is to detect
whether the host supports shadowing of huge gtt pages. If host does
support it, remove the page sizes restriction for vGPU.

Signed-off-by: Changbin Du <[e-mail]>
Reviewed-by: Joonas Lahtinen <[e-mail]>
Signed-off-by: Joonas Lahtinen <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/i915_gem.c

···
 {
 	int ret;
 
-	/*
-	 * We need to fallback to 4K pages since gvt gtt handling doesn't
-	 * support huge page entries - we will need to check either hypervisor
-	 * mm can support huge guest page or just do emulation in gvt.
-	 */
-	if (intel_vgpu_active(dev_priv))
+	/* We need to fallback to 4K pages if host doesn't support huge gtt. */
+	if (intel_vgpu_active(dev_priv) && !intel_vgpu_has_huge_gtt(dev_priv))
 		mkwrite_device_info(dev_priv)->page_sizes =
 			I915_GTT_PAGE_SIZE_4K;
 

drivers/gpu/drm/i915/i915_pvinfo.h

···
  */
 #define VGT_CAPS_FULL_48BIT_PPGTT	BIT(2)
 #define VGT_CAPS_HWSP_EMULATION		BIT(3)
+#define VGT_CAPS_HUGE_GTT		BIT(4)
 
 struct vgt_if {
 	u64 magic;		/* VGT_MAGIC */

drivers/gpu/drm/i915/i915_vgpu.h

···
 	return dev_priv->vgpu.caps & VGT_CAPS_HWSP_EMULATION;
 }
 
+static inline bool
+intel_vgpu_has_huge_gtt(struct drm_i915_private *dev_priv)
+{
+	return dev_priv->vgpu.caps & VGT_CAPS_HUGE_GTT;
+}
+
 int intel_vgt_balloon(struct drm_i915_private *dev_priv);
 void intel_vgt_deballoon(struct drm_i915_private *dev_priv);