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

[Ghimiray, Himal Prasad]

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 ?

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