[PATCH 1/4] drm/xe/vm: Validate userptr during gpu vma prefetching

[Matthew Brost]

On Wed, Feb 26, 2025 at 04:33:41PM +0100, Thomas Hellström wrote:
> If a userptr vma subject to prefetching was already invalidated
> or invalidated during the prefetch operation, the operation would
> repeatedly return -EAGAIN which would typically cause an infinite
> loop.
> 
> Validate the userptr to ensure this doesn't happen.
> 
> Fixes: 5bd24e78829a ("drm/xe/vm: Subclass userptr vmas")
> Fixes: 617eebb9c480 ("drm/xe: Fix array of binds")
> Cc: Matthew Brost <matthew.brost at intel.com>
> Cc: <stable at vger.kernel.org> # v6.9+
> Suggested-by: Matthew Brost <matthew.brost at intel.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> ---
>  drivers/gpu/drm/xe/xe_vm.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 996000f2424e..4c1ca47667ad 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -2307,7 +2307,14 @@ static int vm_bind_ioctl_ops_parse(struct xe_vm *vm, struct drm_gpuva_ops *ops,
>  		}
>  		case DRM_GPUVA_OP_UNMAP:
>  		case DRM_GPUVA_OP_PREFETCH:
> -			/* FIXME: Need to skip some prefetch ops */

The UNMAP case statement is falling through to pretech case which I
believe is not the intent.

So I think:

case DRM_GPUVA_OP_UNMAP:
	xe_vma_ops_incr_pt_update_ops(vops, op->tile_mask);
	break;
case DRM_GPUVA_OP_PREFETCH:
	<new code>

Matt

> +			vma = gpuva_to_vma(op->base.prefetch.va);
> +
> +			if (xe_vma_is_userptr(vma)) {
> +				err = xe_vma_userptr_pin_pages(to_userptr_vma(vma));
> +				if (err)
> +					return err;
> +			}
> +
>  			xe_vma_ops_incr_pt_update_ops(vops, op->tile_mask);
>  			break;
>  		default:
> -- 
> 2.48.1
>