Re: [PATCH v3 1/2] drm/xe/uapi: disallow bind queue sharing

[Matthew Auld <matthew.auld@intel.com>]

On 19/12/2025 06:36, Zhang, Carl wrote:
> 
> 
>> -----Original Message-----
>> From: Brost, Matthew <matthew.brost@intel.com>
>> Sent: Friday, December 19, 2025 4:41 AM
>> To: Auld, Matthew <matthew.auld@intel.com>
>> Cc: Lucas De Marchi <lucas.demarchi@intel.com>; intel-
>> xe@lists.freedesktop.org; Thomas Hellström
>> <thomas.hellstrom@linux.intel.com>; Souza, Jose <jose.souza@intel.com>;
>> Mrozek, Michal <michal.mrozek@intel.com>; Zhang, Carl
>> <carl.zhang@intel.com>; stable@vger.kernel.org
>> Subject: Re: [PATCH v3 1/2] drm/xe/uapi: disallow bind queue sharing
>>
>> On Mon, Nov 24, 2025 at 01:41:55PM +0000, Matthew Auld wrote:
>>> On 20/11/2025 15:34, Lucas De Marchi wrote:
>>>> On Thu, Nov 20, 2025 at 01:27:29PM +0000, Matthew Auld wrote:
>>>>> Currently this is very broken if someone attempts to create a bind
>>>>> queue and share it across multiple VMs. For example currently we
>>>>> assume it is safe to acquire the user VM lock to protect some of
>>>>> the bind queue state, but if allow sharing the bind queue with
>>>>> multiple VMs then this quickly breaks down.
>>>>>
>>>>> To fix this reject using a bind queue with any VM that is not the
>>>>> same VM that was originally passed when creating the bind queue.
>>>>> This a uAPI change, however this was more of an oversight on
>>>>> kernel side that we didn't reject this, and expectation is that
>>>>> userspace shouldn't be using bind queues in this way, so in theory this
>> change should go unnoticed.
>>>>>
>>>>> Based on a patch from Matt Brost.
>>>>>
>>>>> v2 (Matt B):
>>>>>   - Hold the vm lock over queue create, to ensure it can't be
>>>>> closed as
>>>>>     we attach the user_vm to the queue.
>>>>>   - Make sure we actually check for NULL user_vm in destruction path.
>>>>> v3:
>>>>>   - Fix error path handling.
>>>>>
>>>>> Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel
>>>>> GPUs")
>>>>> Reported-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>>>> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
>>>>> Cc: José Roberto de Souza <jose.souza@intel.com>
>>>>> Cc: Matthew Brost <matthew.brost@intel.com>
>>>>> Cc: Michal Mrozek <michal.mrozek@intel.com>
>>>>> Cc: Carl Zhang <carl.zhang@intel.com>
>>>>> Cc: <stable@vger.kernel.org> # v6.8+
>>>>
>>>> we never had any platform officially supported back in 6.8. Let's
>>>> make it 6.12 to avoid useless backporting work.
>>>>
>>>>> Acked-by: José Roberto de Souza <jose.souza@intel.com>
>>>>
>>>> Michal / Carl, can you also ack compute/media are ok with this change?
>>>
> I am ok , current media driver only use default 0,  did not create bind exec queue .

Thanks for confirming.

Michal, ping on this from compute POV?

> 
>>> Ping on this? I did a cursory grep for DRM_XE_ENGINE_CLASS_VM_BIND and
>>> found no users in compute-runtime or media-driver in upstream. This
>>> change should only be noticeable if you directly use
>>> DRM_XE_ENGINE_CLASS_VM_BIND to create a dedicated bind queue, which
>> you then pass into vm_bind.
>>>
>>
>> Yes, ping? It would be good to get this series in.
>>
>> Matt
>>
>>>>
>>>> Lucas De Marchi
>>>
> Thanks
> Carl