linux-kernel - [PATCH 5.9 253/391] drm/i915: Force VTd workarounds when running as a guest OS

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Date:   Tue,  3 Nov 2020 21:35:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stefan Fritsch <sf@...itsch.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>
Subject: [PATCH 5.9 253/391] drm/i915: Force VTd workarounds when running as a guest OS

From: Chris Wilson <chris@...is-wilson.co.uk>

commit 8195400f7ea95399f721ad21f4d663a62c65036f upstream.

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 <sf@...itsch.de>
Suggested-by: Stefan Fritsch <sf@...itsch.de>
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Zhenyu Wang <zhenyuw@...ux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc: Stefan Fritsch <sf@...itsch.de>
Cc: stable@...r.kernel.org
Tested-by: Stefan Fritsch <sf@...itsch.de>
Reviewed-by: Zhenyu Wang <zhenyuw@...ux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201019101523.4145-1-chris@chris-wilson.co.uk
(cherry picked from commit f566fdcd6cc49a9d5b5d782f56e3e7cb243f01b8)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/i915_drv.h |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- 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>
@@ -1716,7 +1718,9 @@ 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)