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    Subject[PATCH 4.14 083/125] drm/i915: Force VTd workarounds when running as a guest OS
    Date
    From: Chris Wilson <chris@chris-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@sfritsch.de>
    Suggested-by: Stefan Fritsch <sf@sfritsch.de>
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
    Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
    Cc: Stefan Fritsch <sf@sfritsch.de>
    Cc: stable@vger.kernel.org
    Tested-by: Stefan Fritsch <sf@sfritsch.de>
    Reviewed-by: Zhenyu Wang <zhenyuw@linux.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@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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>
    @@ -3141,7 +3143,9 @@ 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)

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