[PATCH v2 1/1] drm/xe: Disable compression on SVM

[Matthew Brost]

On Wed, Aug 06, 2025 at 12:25:03PM +0530, Ghimiray, Himal Prasad wrote:
> 
> 
> On 06-08-2025 03:36, Matthew Brost wrote:
> > This is not yet supported, forcefully disable by setting pat_index to
> > zero for CPU address mirror VMAs.
> > 
> > v2:
> >   - Use XE_CACHE_WB (Auld)
> >   - Only modify pat_index if compressed (Himal)
> > 
> > Cc: stable at vger.kernel.org
> > Fixes: b43e864af0d4 ("drm/xe/uapi: Add DRM_XE_VM_BIND_FLAG_CPU_ADDR_MIRROR")
> > Signed-off-by: Matthew Brost <matthew.brost at intel.com>
> > ---
> >   drivers/gpu/drm/xe/xe_pat.c | 10 ++++++++++
> >   drivers/gpu/drm/xe/xe_pat.h | 10 ++++++++++
> >   drivers/gpu/drm/xe/xe_vm.c  |  7 ++++++-
> >   3 files changed, 26 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/xe/xe_pat.c b/drivers/gpu/drm/xe/xe_pat.c
> > index 2e7cb99ae87a..ac1767c812aa 100644
> > --- a/drivers/gpu/drm/xe/xe_pat.c
> > +++ b/drivers/gpu/drm/xe/xe_pat.c
> > @@ -154,6 +154,16 @@ static const struct xe_pat_table_entry xe2_pat_table[] = {
> >   static const struct xe_pat_table_entry xe2_pat_ats = XE2_PAT( 0, 0, 0, 0, 3, 3 );
> >   static const struct xe_pat_table_entry xe2_pat_pta = XE2_PAT( 0, 0, 0, 0, 3, 0 );
> > +bool xe_pat_index_get_comp_mode(struct xe_device *xe, u16 pat_index)
> > +{
> > +	WARN_ON(pat_index >= xe->pat.n_entries);
> > +
> > +	if (xe->pat.table != xe2_pat_table)
> > +		return false;
> > +
> > +	return xe->pat.table[pat_index].value & XE2_COMP_EN;
> > +}
> > +
> >   u16 xe_pat_index_get_coh_mode(struct xe_device *xe, u16 pat_index)
> >   {
> >   	WARN_ON(pat_index >= xe->pat.n_entries);
> > diff --git a/drivers/gpu/drm/xe/xe_pat.h b/drivers/gpu/drm/xe/xe_pat.h
> > index fa0dfbe525cd..8be2856a73af 100644
> > --- a/drivers/gpu/drm/xe/xe_pat.h
> > +++ b/drivers/gpu/drm/xe/xe_pat.h
> > @@ -58,4 +58,14 @@ void xe_pat_dump(struct xe_gt *gt, struct drm_printer *p);
> >    */
> >   u16 xe_pat_index_get_coh_mode(struct xe_device *xe, u16 pat_index);
> > +/**
> > + * xe_pat_index_get_comp_mode() = Extract the compression mode for the given
> > + * pat_index.
> > + * @xe: xe device
> > + * @pat_index: The pat_index to query
> > + *
> > + * Return: True if pat_index is compressed, False otherwise
> > + */
> > +bool xe_pat_index_get_comp_mode(struct xe_device *xe, u16 pat_index);
> > +
> >   #endif
> > diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> > index 432ea325677d..83f507ea7f30 100644
> > --- a/drivers/gpu/drm/xe/xe_vm.c
> > +++ b/drivers/gpu/drm/xe/xe_vm.c
> > @@ -2362,7 +2362,12 @@ vm_bind_ioctl_ops_create(struct xe_vm *vm, struct xe_vma_ops *vops,
> >   			op->map.is_cpu_addr_mirror = flags &
> >   				DRM_XE_VM_BIND_FLAG_CPU_ADDR_MIRROR;
> >   			op->map.dumpable = flags & DRM_XE_VM_BIND_FLAG_DUMPABLE;
> > -			op->map.pat_index = pat_index;
> > +			/* XXX: We don't support SVM + compression yet */
> > +			if (op->map.is_cpu_addr_mirror &&
> > +			    xe_pat_index_get_comp_mode(vm->xe, pat_index))
> > +				op->map.pat_index = vm->xe->pat.idx[XE_CACHE_WB];
> > +			else
> > +				op->map.pat_index = pat_index;
> 
> A warn to let user now compression pat is not supported for
> DRM_XE_VM_BIND_FLAG_CPU_ADDR_MIRROR and kernel is sanitizing it ?
> 

Or do we just nack this at the IOCTL? We have already upstreamed this
uAPI so unsure if that is possible or if that is desired considering we
will likely enable this support at some point. Let's see the maintainers
think? If the code is left as is, I agree a debug/warning message would
be a good idea.

Matt

> >   			op->map.invalidate_on_bind =
> >   				__xe_vm_needs_clear_scratch_pages(vm, flags);
> >   		} else if (__op->op == DRM_GPUVA_OP_PREFETCH) {
>