Re: [PATCH 1/3] drm/i915: Fix command parser to validate multiple register access with the same command.

[Francisco Jerez <currojerez@riseup.net>]

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Francisco Jerez <currojerez@riseup.net> writes:

> Daniel Vetter <daniel@ffwll.ch> writes:
>
>> On Mon, Jun 15, 2015 at 02:26:22PM +0300, Ville Syrjälä wrote:
>>> On Mon, Jun 15, 2015 at 02:18:01PM +0300, Francisco Jerez wrote:
>>> > Daniel Vetter <daniel@ffwll.ch> writes:
>>> > 
>>> > > On Tue, Jun 02, 2015 at 05:36:26PM +0800, Zhigang Gong wrote:
>>> > >> The patchset LGTM and works well with beignet. The 80%+ performance regression issue in darktable also has been fixed
>>> > >> after this patchset applied and enable the atomic in L3 at beignet side. So,
>>> > >> 
>>> > >> Reviewed-by: Zhigang Gong <zhigang.gong@linux.intel.com>
>>> > >
>>> > > All three merged.
>>> > 
>>> > Thanks Daniel.
>>> > 
>>> > > Aside: Dont we need an increment for the cmd parser version for
>>> > > userspace to be able to detect this?
>>> > >
>>> > Yeah, that would be a good idea, patch attached.
>>> 
>>> The old version alloweed userspace to write basically any register, the
>>> new version allows only the whitelisted registers. I don't see how a
>>> version number bump would help anyone.
>>
>> Oops, totally missed the context of patch 1. Jani I think that one's for
>> you too ...
>>
> IMHO the version bump is still useful for userspace to find out whether
> it can use plain LRIs to write the L3 atomic chicken bits.  It's true
> that as Ville said it would have been possible for userspace to write
> the same bits before this series by building a batch specifically
> crafted to cheat the command parser, but I don't think we want userspace
> to rely on a command parser bug (e.g. because we may want to back-port
> the fix to earlier kernel versions).
>
Ping.  I cannot use these registers from userspace until the command
parser version number is bumped.

>> Thanks for pointing this out.
>> -Daniel
>> -- 
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch
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