drm/i915: Force VT'd workarounds when running as a guest OS

If i915.ko is being used as a passthrough device, it does not know if
the host is using intel_iommu. Mixing the iommu and gfx causes a few
issues (such as scanout overfetch) which we need to workaround inside
the driver, so if we detect we are running under a hypervisor, also
assume the device access is being virtualised.

Reported-by: Stefan Fritsch <[email protected]>
Suggested-by: Stefan Fritsch <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Cc: Zhenyu Wang <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Stefan Fritsch <[email protected]>
Cc: [email protected]
Tested-by: Stefan Fritsch <[email protected]>
Reviewed-by: Zhenyu Wang <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit f566fdcd6cc49a9d5b5d782f56e3e7cb243f01b8)
Signed-off-by: Rodrigo Vivi <[email protected]>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index eef9a821c49cd98b27bd7e1c9ac439916d4e4711..8426d59746693f0151034c7dad9bc3f2e1bbb529 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -33,6 +33,8 @@
 #include <uapi/drm/i915_drm.h>
 #include <uapi/drm/drm_fourcc.h>
 
+#include <asm/hypervisor.h>
+
 #include <linux/io-mapping.h>
 #include <linux/i2c.h>
 #include <linux/i2c-algo-bit.h>
@@ -1760,7 +1762,9 @@ static inline bool intel_vtd_active(void)
        if (intel_iommu_gfx_mapped)
                return true;
 #endif
-       return false;
+
+       /* Running as a guest, we assume the host is enforcing VT'd */
+       return !hypervisor_is_type(X86_HYPER_NATIVE);
 }
 
 static inline bool intel_scanout_needs_vtd_wa(struct drm_i915_private *dev_priv)