Re: [PATCH v2 2/2] drm/xe: Allow mixed mappings for userptr

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Acked-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Den 2025-10-14 kl. 13:08, skrev Thomas Hellström:
> + dri-devel.
> 
> From: Matthew Brost <matthew.brost@intel.com>
> 
> Compute kernels often issue memory copies immediately after completion.
> If the memory being copied is an SVM pointer that was faulted into the
> device and then bound via userptr, it is undesirable to move that
> memory. Worse, if userptr is mixed between system and device memory,
> the
> bind operation may be rejected.
> 
> Xe already has the necessary plumbing to support userptr with mixed
> mappings. This update modifies GPUSVM's get_pages to correctly locate
> pages in such mixed mapping scenarios.
> 
> v2:
> - Rebase (Thomas Hellström)
> v3:
> - Remove Fixes tag.
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Reviewed-by: Matthew Auld <matthew.auld@intel.com>
> ---
>  drivers/gpu/drm/drm_gpusvm.c    | 6 ++++--
>  drivers/gpu/drm/xe/xe_userptr.c | 4 +++-
>  include/drm/drm_gpusvm.h        | 4 ++++
>  3 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gpusvm.c
> b/drivers/gpu/drm/drm_gpusvm.c
> index cb906765897e..73e550c8ff8c 100644
> --- a/drivers/gpu/drm/drm_gpusvm.c
> +++ b/drivers/gpu/drm/drm_gpusvm.c
> @@ -1363,7 +1363,8 @@ int drm_gpusvm_get_pages(struct drm_gpusvm
> *gpusvm,
>  		order = drm_gpusvm_hmm_pfn_to_order(pfns[i], i,
> npages);
>  		if (is_device_private_page(page) ||
>  		    is_device_coherent_page(page)) {
> -			if (zdd != page->zone_device_data && i > 0) {
> +			if (!ctx->allow_mixed &&
> +			    zdd != page->zone_device_data && i > 0) {
>  				err = -EOPNOTSUPP;
>  				goto err_unmap;
>  			}
> @@ -1399,7 +1400,8 @@ int drm_gpusvm_get_pages(struct drm_gpusvm
> *gpusvm,
>  		} else {
>  			dma_addr_t addr;
>  
> -			if (is_zone_device_page(page) || pagemap) {
> +			if (is_zone_device_page(page) ||
> +			    (pagemap && !ctx->allow_mixed)) {
>  				err = -EOPNOTSUPP;
>  				goto err_unmap;
>  			}
> diff --git a/drivers/gpu/drm/xe/xe_userptr.c
> b/drivers/gpu/drm/xe/xe_userptr.c
> index f16e92cd8090..0d9130b1958a 100644
> --- a/drivers/gpu/drm/xe/xe_userptr.c
> +++ b/drivers/gpu/drm/xe/xe_userptr.c
> @@ -3,6 +3,7 @@
>   * Copyright © 2025 Intel Corporation
>   */
>  
> +#include "xe_svm.h"
>  #include "xe_userptr.h"
>  
>  #include <linux/mm.h>
> @@ -54,7 +55,8 @@ int xe_vma_userptr_pin_pages(struct xe_userptr_vma
> *uvma)
>  	struct xe_device *xe = vm->xe;
>  	struct drm_gpusvm_ctx ctx = {
>  		.read_only = xe_vma_read_only(vma),
> -		.device_private_page_owner = NULL,
> +		.device_private_page_owner = xe_svm_devm_owner(xe),
> +		.allow_mixed = true,
>  	};
>  
>  	lockdep_assert_held(&vm->lock);
> diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
> index b92faa9a26b2..632e100e6efb 100644
> --- a/include/drm/drm_gpusvm.h
> +++ b/include/drm/drm_gpusvm.h
> @@ -235,6 +235,9 @@ struct drm_gpusvm {
>   * @read_only: operating on read-only memory
>   * @devmem_possible: possible to use device memory
>   * @devmem_only: use only device memory
> + * @allow_mixed: Allow mixed mappings in get pages. Mixing between
> system and
> + *               single dpagemap is supported, mixing between multiple
> dpagemap
> + *               is unsupported.
>   *
>   * Context that is DRM GPUSVM is operating in (i.e. user arguments).
>   */
> @@ -246,6 +249,7 @@ struct drm_gpusvm_ctx {
>  	unsigned int read_only :1;
>  	unsigned int devmem_possible :1;
>  	unsigned int devmem_only :1;
> +	unsigned int allow_mixed :1;
>  };
>  
>  int drm_gpusvm_init(struct drm_gpusvm *gpusvm,
> 
>