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

[Matthew Brost <matthew.brost@intel.com>]

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?
> 
> 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
>