Re: [PATCH 5/7] drm/xe: Correct migration VM teardown order

["Summers, Stuart" <stuart.summers@intel.com>]

On Wed, 2025-10-22 at 13:30 -0700, Matthew Brost wrote:
> On Mon, Oct 20, 2025 at 09:45:27PM +0000, Stuart Summers wrote:
> > Adjust the sequence of the migration teardown to match what
> > is happening in the init() function.
> > 
> > v2: Take a reference to the migrate queue before put (Matt)
> > 
> 
> You need to store the VM on the stack, not the queue;
> 
> > Signed-off-by: Stuart Summers <stuart.summers@intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_migrate.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_migrate.c
> > b/drivers/gpu/drm/xe/xe_migrate.c
> > index 7345a5b65169..ae42917918e5 100644
> > --- a/drivers/gpu/drm/xe/xe_migrate.c
> > +++ b/drivers/gpu/drm/xe/xe_migrate.c
> > @@ -91,17 +91,18 @@ struct xe_migrate {
> >  static void xe_migrate_fini(void *arg)
> >  {
> >         struct xe_migrate *m = arg;
> > +       struct xe_exec_queue *q = m->q;
> >  
> > -       xe_vm_lock(m->q->vm, false);
> > +       xe_vm_lock(q->vm, false);
> >         xe_bo_unpin(m->pt_bo);
> > -       xe_vm_unlock(m->q->vm);
> > +       xe_vm_unlock(q->vm);
> >  
> >         dma_fence_put(m->fence);
> >         xe_bo_put(m->pt_bo);
> >         drm_suballoc_manager_fini(&m->vm_update_sa);
> >         mutex_destroy(&m->job_mutex);
> > -       xe_vm_close_and_put(m->q->vm);
> > -       xe_exec_queue_put(m->q);
> > +       xe_exec_queue_put(q);
> 
> ^^^ This can destroy the 'q'.
> 
> > +       xe_vm_close_and_put(q->vm);
> 
> ^^^ Now 'q->' can dereference invalid memory.

Bah you're right, sorry about that :(. Thanks for the feedback!

-Stuart

> 
> Matt
> 
> >  }
> >  
> >  static u64 xe_migrate_vm_addr(u64 slot, u32 level)
> > -- 
> > 2.34.1
> >