[Intel-gfx] [PATCH V5] drm/i915: Disable stolen memory when i915 runs on qemu

[Xiong Zhang]

Stolen memory isn't a standard pci resource and exists in RMRR which has
identity mapping in iommu table, IGD could access stolen memory in host OS.
While according to 'commit c875d2c1b808 ("iommu/vt-d: Exclude devices using
RMRRs from IOMMU API domains")',RMRR isn't supported by kvm, then both EPT
and guest iommu domain table lack of maaping for stolen memory in kvm IGD
passthrough environment. If IGD access stolen memory in such environment,
many iommu exceptions exist in host dmesg and gpu hang exists also.
DMAR: [DMA Read] Request device [00:02.0] fault addr da012000
[fault reason 05] PTE Write access is not set
DMAR: [DMA Read] Request device [00:02.0] fault addr da2df000
[fault reason 06] PTE Read access is not set

So stolen memory should be disabled in KVM IGD passthrough environment,
this patch detects such environment through the existence of qemu emulated 
isa bridge.

When the real ISA bridge is also passed through to guest, guest will have
two isa bridges: emulated and real. Qemu guarantees the busnum:devnum.
funcnum of emulated isa bridge is always less than the real one. Then
emulated isa bridge is always detected first by pci_get_class(ISA). So
stolen memory will be disabled in this case also.

Stolen memory exists in kernel for a long time, but this patch depends
on INTEL_PCH_QEMU_DEVICE_ID_TYPE which was introduced in v4.5 kernel,
so this patch should be backported into v4.5 kernel and above.

v2:GVT-g may run in non qemu (Zhenyu)
v3:Make commit message clear (Daniel)
v4:Fix typo
v5:Exclude P2X as it is used for VMware (Joonas)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99028

Signed-off-by: Xiong Zhang <xiong.y.zhang at intel.com>
Reviewed-by: Zhenyu Wang <zhenyuw at linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/i915/i915_drv.c        | 5 +++++
 drivers/gpu/drm/i915/i915_drv.h        | 1 +
 drivers/gpu/drm/i915/i915_gem_stolen.c | 4 ++--
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 6d9944a..0d3c395 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -223,6 +223,11 @@ static void intel_detect_pch(struct drm_i915_private *dev_priv)
 					    PCI_SUBVENDOR_ID_REDHAT_QUMRANET &&
 				    pch->subsystem_device ==
 					    PCI_SUBDEVICE_ID_QEMU)) {
+				/*
+				 * P2X is used for VMware, exclude it
+				 */
+				if (id != INTEL_PCH_P2X_DEVICE_ID_TYPE)
+					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 2911c49..c87150e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2152,6 +2152,7 @@ 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;
 	}
 
-- 
2.9.3