[PATCH V3] drm/i915: Enhanced disable access to stolen memory as a guest

[Xiong Zhang <xiong.y.zhang@intel.com>]

Stolen memroy is in RMRR and have identity mapping in iommu, so
gt could access stolen memory in host OS. While RMRR isn't supported
in kvm, both EPT and guest iommu domain lack of maaping for stolen memory,
so both vcpu an gt couldn't access stolen memroy in guest.

commit "04a68a3 drm/i915/gvt: Disable access to stolen memory as a guest"
isn't enough in IGD passthrough environment where vgt code don't run. This
patch detects i915 running as a guest through the existence of emulated ISA
bridge.

v2:GVT-g may run in non qemu (Zhenyu)

References: c875d2c iommu/vt-d: Exclude devices using RMRRs from IOMMU API domains
Link: https://access.redhat.com/sites/default/files/attachments/rmrr-wp1.pdf
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99028

Signed-off-by: Xiong Zhang <xiong.y.zhang@intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/i915/i915_drv.c        | 1 +
 drivers/gpu/drm/i915/i915_drv.h        | 1 +
 drivers/gpu/drm/i915/i915_gem_stolen.c | 4 ++--
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 03d9e45..8b807a9 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -223,6 +223,7 @@ static void intel_detect_pch(struct drm_i915_private *dev_priv)
 					    PCI_SUBVENDOR_ID_REDHAT_QUMRANET &&
 				    pch->subsystem_device ==
 					    PCI_SUBDEVICE_ID_QEMU)) {
+				dev_priv->run_on_qemu = true;
 				dev_priv->pch_type =
 					intel_virt_detect_pch(dev_priv);
 			} else
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index a5947a4..ad95c87 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2145,6 +2145,7 @@ struct drm_i915_private {
 	struct intel_uncore uncore;
 
 	struct i915_virtual_gpu vgpu;
+	bool run_on_qemu;
 
 	struct intel_gvt *gvt;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index f3abdc2..6a011b0 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -409,8 +409,8 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
 
 	mutex_init(&dev_priv->mm.stolen_lock);
 
-	if (intel_vgpu_active(dev_priv)) {
-		DRM_INFO("iGVT-g active, disabling use of stolen memory\n");
+	if (dev_priv->run_on_qemu || intel_vgpu_active(dev_priv)) {
+		DRM_INFO("Running in guest, disabling use of stolen memory\n");
 		return 0;
 	}
 
-- 
1.9.1