Re: [PATCH] drm/xe: Unmap userptr in MMU invalidation notifier

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Mon, 2024-04-29 at 01:11 +0000, Matthew Brost wrote:
> On Fri, Apr 26, 2024 at 04:32:36PM -0700, Matthew Brost wrote:
> > To be secure, when a userptr is invalidated the pages should be dma
> > unmapped ensuring the device can no longer touch the invalidated
> > pages.
> > 
> > Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel
> > GPUs")
> > Fixes: 12f4b58a37f4 ("drm/xe: Use hmm_range_fault to populate user
> > pages")
> > Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > Cc: stable@vger.kernel.org # 6.8
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_vm.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_vm.c
> > b/drivers/gpu/drm/xe/xe_vm.c
> > index dfd31b346021..964a5b4d47d8 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.c
> > +++ b/drivers/gpu/drm/xe/xe_vm.c
> > @@ -637,6 +637,9 @@ static bool vma_userptr_invalidate(struct
> > mmu_interval_notifier *mni,
> >  		XE_WARN_ON(err);
> >  	}
> >  
> > +	if (userptr->sg)
> > +		xe_hmm_userptr_free_sg(uvma);
> > +
> 
> I thought about this a bit, I think here we only dma unmap the SG,
> not
> free it. Freeing it could cause a current bind walk to access corrupt
> memory. Freeing can be deferred to the next attempt to bind the
> userptr
> or userptr destroy.

Yes, makes sense.
/Thomas



> 
> Matt
> 
> >  	trace_xe_vma_userptr_invalidate_complete(vma);
> >  
> >  	return true;
> > -- 
> > 2.34.1
> >