[Intel-gfx] [PATCH v7 3/5] drm/i915: Use batch length instead of object size in command parser

[Bloomfield, Jon]

> -----Original Message-----
> From: Nguyen, Michael H
> Sent: Thursday, December 11, 2014 8:13 PM
> To: intel-gfx at lists.freedesktop.org
> Cc: Bloomfield, Jon; Brad Volkin
> Subject: [PATCH v7 3/5] drm/i915: Use batch length instead of object size in
> command parser
> 
> From: Brad Volkin <bradley.d.volkin at intel.com>
> 
> Previously we couldn't trust the user-supplied batch length because it came
> directly from userspace (i.e. untrusted code). It would have affected what
> commands software parsed without regard to what hardware would actually
> execute, leaving a potential hole.
> 
> With the parser now copying the user supplied batch buffer and writing
> MI_NOP commands to any space after the copied region, we can safely use
> the batch length input. This should be a performance win as the actual batch
> length is frequently much smaller than the allocated object size.
> 
> v2: Fix handling of non-zero batch_start_offset
> 
> Issue: VIZ-4719
> Signed-off-by: Brad Volkin <bradley.d.volkin at intel.com>

Reviewed-by: Jon Bloomfield <jon.bloomfield at intel.com>