[Intel-gfx] [PATCH] drm/i915: Fix cmd parser desc matching with masks

[Chris Wilson]

Quoting Mika Kuoppala (2020-08-17 20:59:26)
> Our variety of defined gpu commands have the actual
> command id field and possibly length and flags applied.
> 
> We did start to apply the mask during initialization of
> the cmd descriptors but forgot to also apply it on comparisons.
> 
> Fix comparisons in order to properly deny access with
> associated commands.
> 
> v2: fix lri with correct mask (Chris)
> 
> References: 926abff21a8f ("drm/i915/cmdparser: Ignore Length operands during command matching")
> Reported-by: Nicolai Stange <nstange at suse.de>
> Cc: stable at vger.kernel.org # v5.4+
> Cc: Miroslav Benes <mbenes at suse.cz>
> Cc: Takashi Iwai <tiwai at suse.de>
> Cc: Tyler Hicks <tyhicks at canonical.com>
> Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> Cc: Chris Wilson <chris.p.wilson at intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_cmd_parser.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 372354d33f55..5ac4a999f05a 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -1204,6 +1204,12 @@ static u32 *copy_batch(struct drm_i915_gem_object *dst_obj,
>         return dst;
>  }
>  
> +static inline bool cmd_desc_is(const struct drm_i915_cmd_descriptor * const desc,
> +                              const u32 cmd)
> +{
> +       return desc->cmd.value == (cmd & desc->cmd.mask);

We could observe that the mask we need is always -1u << 23, we do use
that info already for the cmd hashing, but more important is that we are
consistent with our use of desc->cmd.mask everywhere else.

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris
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