On Thu, 13 Dec 2018, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
> We've supported the opregion RVDA/RVDS fields for VBT size >= 6 KB since
> commit 04ebaadb9f2d ("drm/i915/opregion: handle VBT sizes bigger than 6
> KB"). That's three years, almost to the date.
>
> The implementation was based on spec only, in anticipation of systems
> with big VBT. Now, the spec has been changed. The RVDA is supposed to be
> relative from the beginning of opregion, not absolute address.
>
> This is obviously a backward/forward incompatible change. I've been told
> there are no systems out there using the field. Fingers crossed. This
> will still be problematic for older kernels, and we can only try to
> backport the fix.
Should add this to the commit message:
While at it, add the missing memunmap() on the failure path for
completeness.
>
> Fixes: 04ebaadb9f2d ("drm/i915/opregion: handle VBT sizes bigger than 6 KB")
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_opregion.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
> index b8f106d9ecf8..700fddaa8d9e 100644
> --- a/drivers/gpu/drm/i915/intel_opregion.c
> +++ b/drivers/gpu/drm/i915/intel_opregion.c
> @@ -119,7 +119,7 @@ struct opregion_asle {
> u64 fdss;
> u32 fdsp;
> u32 stat;
> - u64 rvda; /* Physical address of raw vbt data */
> + u64 rvda; /* Address of raw vbt data, relative from opregion */
> u32 rvds; /* Size of raw vbt data */
> u8 rsvd[58];
> } __packed;
> @@ -955,7 +955,13 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
>
> if (opregion->header->opregion_ver >= 2 && opregion->asle &&
> opregion->asle->rvda && opregion->asle->rvds) {
> - opregion->rvda = memremap(opregion->asle->rvda,
> + /*
> + * rvda is unsigned, relative from opregion base, and should
> + * never point within opregion.
> + */
> + WARN_ON(opregion->asle->rvda < OPREGION_SIZE);
> +
> + opregion->rvda = memremap(asls + opregion->asle->rvda,
> opregion->asle->rvds,
> MEMREMAP_WB);
> vbt = opregion->rvda;
> @@ -967,6 +973,8 @@ int intel_opregion_setup(struct drm_i915_private *dev_priv)
> goto out;
> } else {
> DRM_DEBUG_KMS("Invalid VBT in ACPI OpRegion (RVDA)\n");
> + memunmap(opregion->rvda);
> + opregion->rvda = NULL;
> }
> }
--
Jani Nikula, Intel Open Source Graphics Center
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