Re: [PATCH v4 21/33] drm/xe: Add SVM device memory mirroring

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

On Wed, 2025-01-29 at 11:52 -0800, Matthew Brost wrote:
> Add SVM device memory mirroring which enables device pages for
> migration. Enabled via CONFIG_XE_DEVMEM_MIRROR Kconfig. Kconfig
> option
> defaults to enabled. If not enabled, SVM will work sans migration and
> KMD memory footprint will be less.
> 
> v3:
>  - Add CONFIG_XE_DEVMEM_MIRROR
> v4:
>  - Fix Kconfig (Himal)
>  - Use %pe to print errors (Thomas)
>  - Fix alignment issue (Checkpatch)
> 
> Signed-off-by: Niranjana Vishwanathapura
> <niranjana.vishwanathapura@intel.com>
> Signed-off-by: Oak Zeng <oak.zeng@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

> ---
>  drivers/gpu/drm/xe/Kconfig           |  9 ++++
>  drivers/gpu/drm/xe/xe_device_types.h |  8 ++++
>  drivers/gpu/drm/xe/xe_svm.c          | 62
> +++++++++++++++++++++++++++-
>  drivers/gpu/drm/xe/xe_svm.h          |  3 ++
>  drivers/gpu/drm/xe/xe_tile.c         |  5 +++
>  5 files changed, 85 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/Kconfig b/drivers/gpu/drm/xe/Kconfig
> index 60b922f75001..4bc03d6f6720 100644
> --- a/drivers/gpu/drm/xe/Kconfig
> +++ b/drivers/gpu/drm/xe/Kconfig
> @@ -74,6 +74,15 @@ config DRM_XE_DP_TUNNEL
>  
>  	  If in doubt say "Y".
>  
> +config DRM_XE_DEVMEM_MIRROR
> +	bool "Enable device memory mirror"
> +	depends on DRM_XE
> +	select GET_FREE_REGION
> +	default y
> +	help
> +	  Disable this option only if you want to compile out
> without device
> +	  memory mirror. Will reduce KMD memory footprint when
> disabled.
> +
>  config DRM_XE_FORCE_PROBE
>  	string "Force probe xe for selected Intel hardware IDs"
>  	depends on DRM_XE
> diff --git a/drivers/gpu/drm/xe/xe_device_types.h
> b/drivers/gpu/drm/xe/xe_device_types.h
> index 71151532e28f..da5bf145324b 100644
> --- a/drivers/gpu/drm/xe/xe_device_types.h
> +++ b/drivers/gpu/drm/xe/xe_device_types.h
> @@ -104,6 +104,14 @@ struct xe_mem_region {
>  	resource_size_t actual_physical_size;
>  	/** @mapping: pointer to VRAM mappable space */
>  	void __iomem *mapping;
> +	/** @pagemap: Used to remap device memory as ZONE_DEVICE */
> +	struct dev_pagemap pagemap;
> +	/**
> +	 * @hpa_base: base host physical address
> +	 *
> +	 * This is generated when remap device memory as ZONE_DEVICE
> +	 */
> +	resource_size_t hpa_base;
>  };
>  
>  /**
> diff --git a/drivers/gpu/drm/xe/xe_svm.c
> b/drivers/gpu/drm/xe/xe_svm.c
> index ee150139470f..985ac20c5b07 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -19,6 +19,11 @@ static struct xe_vm *range_to_vm(struct
> drm_gpusvm_range *r)
>  	return gpusvm_to_vm(r->gpusvm);
>  }
>  
> +static void *xe_svm_devm_owner(struct xe_device *xe)
> +{
> +	return xe;
> +}
> +
>  static struct drm_gpusvm_range *
>  xe_svm_range_alloc(struct drm_gpusvm *gpusvm)
>  {
> @@ -307,8 +312,8 @@ int xe_svm_init(struct xe_vm *vm)
>  		  xe_svm_garbage_collector_work_func);
>  
>  	err = drm_gpusvm_init(&vm->svm.gpusvm, "Xe SVM", &vm->xe-
> >drm,
> -			      current->mm, NULL, 0, vm->size,
> -			      SZ_512M, &gpusvm_ops,
> fault_chunk_sizes,
> +			      current->mm, xe_svm_devm_owner(vm-
> >xe), 0,
> +			      vm->size, SZ_512M, &gpusvm_ops,
> fault_chunk_sizes,
>  			      ARRAY_SIZE(fault_chunk_sizes));
>  	if (err)
>  		return err;
> @@ -443,3 +448,56 @@ bool xe_svm_has_mapping(struct xe_vm *vm, u64
> start, u64 end)
>  {
>  	return drm_gpusvm_has_mapping(&vm->svm.gpusvm, start, end);
>  }
> +
> +#if IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR)
> +/**
> + * xe_devm_add: Remap and provide memmap backing for device memory
> + * @tile: tile that the memory region belongs to
> + * @mr: memory region to remap
> + *
> + * This remap device memory to host physical address space and
> create
> + * struct page to back device memory
> + *
> + * Return: 0 on success standard error code otherwise
> + */
> +int xe_devm_add(struct xe_tile *tile, struct xe_mem_region *mr)
> +{
> +	struct xe_device *xe = tile_to_xe(tile);
> +	struct device *dev = &to_pci_dev(xe->drm.dev)->dev;
> +	struct resource *res;
> +	void *addr;
> +	int ret;
> +
> +	res = devm_request_free_mem_region(dev, &iomem_resource,
> +					   mr->usable_size);
> +	if (IS_ERR(res)) {
> +		ret = PTR_ERR(res);
> +		return ret;
> +	}
> +
> +	mr->pagemap.type = MEMORY_DEVICE_PRIVATE;
> +	mr->pagemap.range.start = res->start;
> +	mr->pagemap.range.end = res->end;
> +	mr->pagemap.nr_range = 1;
> +	mr->pagemap.ops = drm_gpusvm_pagemap_ops_get();
> +	mr->pagemap.owner = xe_svm_devm_owner(xe);
> +	addr = devm_memremap_pages(dev, &mr->pagemap);
> +	if (IS_ERR(addr)) {
> +		devm_release_mem_region(dev, res->start,
> resource_size(res));
> +		ret = PTR_ERR(addr);
> +		drm_err(&xe->drm, "Failed to remap tile %d memory,
> errno %pe\n",
> +			tile->id, ERR_PTR(ret));
> +		return ret;
> +	}
> +	mr->hpa_base = res->start;
> +
> +	drm_info(&xe->drm, "Added tile %d memory [%llx-%llx] to
> devm, remapped to %pr\n",
> +		 tile->id, mr->io_start, mr->io_start + mr-
> >usable_size, res);
> +	return 0;
> +}
> +#else
> +int xe_devm_add(struct xe_tile *tile, struct xe_mem_region *mr)
> +{
> +	return 0;
> +}
> +#endif
> diff --git a/drivers/gpu/drm/xe/xe_svm.h
> b/drivers/gpu/drm/xe/xe_svm.h
> index b181c174ca61..63daffdfdbf6 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -11,6 +11,7 @@
>  
>  #define XE_INTERCONNECT_VRAM DRM_INTERCONNECT_DRIVER
>  
> +struct xe_mem_region;
>  struct xe_tile;
>  struct xe_vm;
>  struct xe_vma;
> @@ -36,6 +37,8 @@ struct xe_svm_range {
>  	u8 tile_invalidated;
>  };
>  
> +int xe_devm_add(struct xe_tile *tile, struct xe_mem_region *mr);
> +
>  int xe_svm_init(struct xe_vm *vm);
>  
>  void xe_svm_fini(struct xe_vm *vm);
> diff --git a/drivers/gpu/drm/xe/xe_tile.c
> b/drivers/gpu/drm/xe/xe_tile.c
> index 2825553b568f..6c80a637ded5 100644
> --- a/drivers/gpu/drm/xe/xe_tile.c
> +++ b/drivers/gpu/drm/xe/xe_tile.c
> @@ -13,6 +13,7 @@
>  #include "xe_migrate.h"
>  #include "xe_pcode.h"
>  #include "xe_sa.h"
> +#include "xe_svm.h"
>  #include "xe_tile.h"
>  #include "xe_tile_sysfs.h"
>  #include "xe_ttm_vram_mgr.h"
> @@ -164,6 +165,7 @@ static int tile_ttm_mgr_init(struct xe_tile
> *tile)
>   */
>  int xe_tile_init_noalloc(struct xe_tile *tile)
>  {
> +	struct xe_device *xe = tile_to_xe(tile);
>  	int err;
>  
>  	err = tile_ttm_mgr_init(tile);
> @@ -172,6 +174,9 @@ int xe_tile_init_noalloc(struct xe_tile *tile)
>  
>  	xe_wa_apply_tile_workarounds(tile);
>  
> +	if (xe->info.has_usm && IS_DGFX(xe))
> +		xe_devm_add(tile, &tile->mem.vram);
> +
>  	err = xe_tile_sysfs_init(tile);
>  
>  	return 0;