[PATCH v2 3/3] drm/xe: Implement and use the drm_pagemap populate_mm op

Matthew Brost matthew.brost at intel.com
Thu Jun 5 22:16:29 UTC 2025


On Wed, Jun 04, 2025 at 11:35:36AM +0200, Thomas Hellström wrote:
> Add runtime PM since we might call populate_mm on a foreign device.
> Also create the VRAM bos as ttm_bo_type_kernel. This avoids the
> initial clearing and the creation of an mmap handle.
> 

I didn't read this part - skipping the initial clears. Discussed this on
a private chat but to recap we need initial clears as copies for
non-faulted in CPU pages are skipped which could result in another
processes data being exposed in VRAM. We could only issue a clear if a
non-faulted in page is found in xe_svm_copy or IIRC there was some work
flying around to clear VRAM upon free, not sure if that ever landed - I
believe AMD does clear on free their driver + buddy allocator has the
concept of dirty blocks.

Matt 

> Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> ---
>  drivers/gpu/drm/drm_pagemap.c |   1 +
>  drivers/gpu/drm/xe/xe_svm.c   | 104 ++++++++++++++++++++--------------
>  drivers/gpu/drm/xe/xe_svm.h   |  10 ++--
>  drivers/gpu/drm/xe/xe_tile.h  |  11 ++++
>  drivers/gpu/drm/xe/xe_vm.c    |   2 +-
>  5 files changed, 78 insertions(+), 50 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_pagemap.c b/drivers/gpu/drm/drm_pagemap.c
> index 25395685a9b8..94619be00d2a 100644
> --- a/drivers/gpu/drm/drm_pagemap.c
> +++ b/drivers/gpu/drm/drm_pagemap.c
> @@ -843,3 +843,4 @@ int drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
>  
>  	return err;
>  }
> +EXPORT_SYMBOL(drm_pagemap_populate_mm);
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index e161ce3e67a1..a10aab3768d8 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -3,13 +3,17 @@
>   * Copyright © 2024 Intel Corporation
>   */
>  
> +#include <drm/drm_drv.h>
> +
>  #include "xe_bo.h"
>  #include "xe_gt_stats.h"
>  #include "xe_gt_tlb_invalidation.h"
>  #include "xe_migrate.h"
>  #include "xe_module.h"
> +#include "xe_pm.h"
>  #include "xe_pt.h"
>  #include "xe_svm.h"
> +#include "xe_tile.h"
>  #include "xe_ttm_vram_mgr.h"
>  #include "xe_vm.h"
>  #include "xe_vm_types.h"
> @@ -525,8 +529,10 @@ static struct xe_bo *to_xe_bo(struct drm_pagemap_devmem *devmem_allocation)
>  static void xe_svm_devmem_release(struct drm_pagemap_devmem *devmem_allocation)
>  {
>  	struct xe_bo *bo = to_xe_bo(devmem_allocation);
> +	struct xe_device *xe = xe_bo_device(bo);
>  
>  	xe_bo_put_async(bo);
> +	xe_pm_runtime_put(xe);
>  }
>  
>  static u64 block_offset_to_pfn(struct xe_vram_region *vr, u64 offset)
> @@ -720,76 +726,63 @@ static struct xe_vram_region *tile_to_vr(struct xe_tile *tile)
>  	return &tile->mem.vram;
>  }
>  
> -/**
> - * xe_svm_alloc_vram()- Allocate device memory pages for range,
> - * migrating existing data.
> - * @vm: The VM.
> - * @tile: tile to allocate vram from
> - * @range: SVM range
> - * @ctx: DRM GPU SVM context
> - *
> - * Return: 0 on success, error code on failure.
> - */
> -int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
> -		      struct xe_svm_range *range,
> -		      const struct drm_gpusvm_ctx *ctx)
> +static int xe_drm_pagemap_populate_mm(struct drm_pagemap *dpagemap,
> +				      unsigned long start, unsigned long end,
> +				      struct mm_struct *mm,
> +				      unsigned long timeslice_ms)
>  {
> -	struct mm_struct *mm = vm->svm.gpusvm.mm;
> +	struct xe_tile *tile = container_of(dpagemap, typeof(*tile), mem.vram.dpagemap);
> +	struct xe_device *xe = tile_to_xe(tile);
> +	struct device *dev = xe->drm.dev;
>  	struct xe_vram_region *vr = tile_to_vr(tile);
>  	struct drm_buddy_block *block;
>  	struct list_head *blocks;
>  	struct xe_bo *bo;
> -	ktime_t end = 0;
> -	int err;
> -
> -	if (!range->base.flags.migrate_devmem)
> -		return -EINVAL;
> +	ktime_t time_end = 0;
> +	int err, idx;
>  
> -	range_debug(range, "ALLOCATE VRAM");
> +	if (!drm_dev_enter(&xe->drm, &idx))
> +		return -ENODEV;
>  
> -	if (!mmget_not_zero(mm))
> -		return -EFAULT;
> -	mmap_read_lock(mm);
> +	xe_pm_runtime_get(xe);
>  
> -retry:
> -	bo = xe_bo_create_locked(tile_to_xe(tile), NULL, NULL,
> -				 xe_svm_range_size(range),
> -				 ttm_bo_type_device,
> + retry:
> +	bo = xe_bo_create_locked(tile_to_xe(tile), NULL, NULL, end - start,
> +				 ttm_bo_type_kernel,
>  				 XE_BO_FLAG_VRAM_IF_DGFX(tile) |
>  				 XE_BO_FLAG_CPU_ADDR_MIRROR);
>  	if (IS_ERR(bo)) {
>  		err = PTR_ERR(bo);
> -		if (xe_vm_validate_should_retry(NULL, err, &end))
> +		if (xe_vm_validate_should_retry(NULL, err, &time_end))
>  			goto retry;
> -		goto unlock;
> +		goto out_pm_put;
>  	}
>  
> -	drm_pagemap_devmem_init(&bo->devmem_allocation,
> -				vm->xe->drm.dev, mm,
> +	drm_pagemap_devmem_init(&bo->devmem_allocation, dev, mm,
>  				&dpagemap_devmem_ops,
>  				&tile->mem.vram.dpagemap,
> -				xe_svm_range_size(range));
> +				end - start);
>  
>  	blocks = &to_xe_ttm_vram_mgr_resource(bo->ttm.resource)->blocks;
>  	list_for_each_entry(block, blocks, link)
>  		block->private = vr;
>  
>  	xe_bo_get(bo);
> -	err = drm_pagemap_migrate_to_devmem(&bo->devmem_allocation,
> -					    mm,
> -					    xe_svm_range_start(range),
> -					    xe_svm_range_end(range),
> -					    ctx->timeslice_ms,
> -					    xe_svm_devm_owner(vm->xe));
> +
> +	/* Ensure the device has a pm ref while there are device pages active. */
> +	xe_pm_runtime_get_noresume(xe);
> +	err = drm_pagemap_migrate_to_devmem(&bo->devmem_allocation, mm,
> +					    start, end, timeslice_ms,
> +					    xe_svm_devm_owner(xe));
>  	if (err)
>  		xe_svm_devmem_release(&bo->devmem_allocation);
>  
>  	xe_bo_unlock(bo);
>  	xe_bo_put(bo);
>  
> -unlock:
> -	mmap_read_unlock(mm);
> -	mmput(mm);
> +out_pm_put:
> +	xe_pm_runtime_put(xe);
> +	drm_dev_exit(idx);
>  
>  	return err;
>  }
> @@ -898,7 +891,7 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
>  
>  	if (--migrate_try_count >= 0 &&
>  	    xe_svm_range_needs_migrate_to_vram(range, vma, IS_DGFX(vm->xe))) {
> -		err = xe_svm_alloc_vram(vm, tile, range, &ctx);
> +		err = xe_svm_alloc_vram(tile, range, &ctx);
>  		ctx.timeslice_ms <<= 1;	/* Double timeslice if we have to retry */
>  		if (err) {
>  			if (migrate_try_count || !ctx.devmem_only) {
> @@ -1054,6 +1047,30 @@ int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range,
>  
>  #if IS_ENABLED(CONFIG_DRM_XE_PAGEMAP)
>  
> +/**
> + * xe_svm_alloc_vram()- Allocate device memory pages for range,
> + * migrating existing data.
> + * @vm: The VM.
> + * @tile: tile to allocate vram from
> + * @range: SVM range
> + * @ctx: DRM GPU SVM context
> + *
> + * Return: 0 on success, error code on failure.
> + */
> +int xe_svm_alloc_vram(struct xe_tile *tile, struct xe_svm_range *range,
> +		      const struct drm_gpusvm_ctx *ctx)
> +{
> +	struct drm_pagemap *dpagemap;
> +
> +	range_debug(range, "ALLOCATE VRAM");
> +
> +	dpagemap = xe_tile_local_pagemap(tile);
> +	return drm_pagemap_populate_mm(dpagemap, xe_svm_range_start(range),
> +				       xe_svm_range_end(range),
> +				       range->base.gpusvm->mm,
> +				       ctx->timeslice_ms);
> +}
> +
>  static struct drm_pagemap_device_addr
>  xe_drm_pagemap_device_map(struct drm_pagemap *dpagemap,
>  			  struct device *dev,
> @@ -1078,6 +1095,7 @@ xe_drm_pagemap_device_map(struct drm_pagemap *dpagemap,
>  
>  static const struct drm_pagemap_ops xe_drm_pagemap_ops = {
>  	.device_map = xe_drm_pagemap_device_map,
> +	.populate_mm = xe_drm_pagemap_populate_mm,
>  };
>  
>  /**
> @@ -1130,7 +1148,7 @@ int xe_devm_add(struct xe_tile *tile, struct xe_vram_region *vr)
>  	return 0;
>  }
>  #else
> -int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
> +int xe_svm_alloc_vram(struct xe_tile *tile,
>  		      struct xe_svm_range *range,
>  		      const struct drm_gpusvm_ctx *ctx)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
> index 19ce4f2754a7..da9a69ea0bb1 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -70,8 +70,7 @@ int xe_svm_bo_evict(struct xe_bo *bo);
>  
>  void xe_svm_range_debug(struct xe_svm_range *range, const char *operation);
>  
> -int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
> -		      struct xe_svm_range *range,
> +int xe_svm_alloc_vram(struct xe_tile *tile, struct xe_svm_range *range,
>  		      const struct drm_gpusvm_ctx *ctx);
>  
>  struct xe_svm_range *xe_svm_range_find_or_insert(struct xe_vm *vm, u64 addr,
> @@ -237,10 +236,9 @@ void xe_svm_range_debug(struct xe_svm_range *range, const char *operation)
>  {
>  }
>  
> -static inline
> -int xe_svm_alloc_vram(struct xe_vm *vm, struct xe_tile *tile,
> -		      struct xe_svm_range *range,
> -		      const struct drm_gpusvm_ctx *ctx)
> +static inline int
> +xe_svm_alloc_vram(struct xe_tile *tile, struct xe_svm_range *range,
> +		  const struct drm_gpusvm_ctx *ctx)
>  {
>  	return -EOPNOTSUPP;
>  }
> diff --git a/drivers/gpu/drm/xe/xe_tile.h b/drivers/gpu/drm/xe/xe_tile.h
> index eb939316d55b..066a3d0cea79 100644
> --- a/drivers/gpu/drm/xe/xe_tile.h
> +++ b/drivers/gpu/drm/xe/xe_tile.h
> @@ -16,4 +16,15 @@ int xe_tile_init(struct xe_tile *tile);
>  
>  void xe_tile_migrate_wait(struct xe_tile *tile);
>  
> +#if IS_ENABLED(CONFIG_DRM_XE_PAGEMAP)
> +static inline struct drm_pagemap *xe_tile_local_pagemap(struct xe_tile *tile)
> +{
> +	return &tile->mem.vram.dpagemap;
> +}
> +#else
> +static inline struct drm_pagemap *xe_tile_local_pagemap(struct xe_tile *tile)
> +{
> +	return NULL;
> +}
> +#endif
>  #endif
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 7140d8856bad..def493acb4d7 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -2911,7 +2911,7 @@ static int prefetch_ranges(struct xe_vm *vm, struct xe_vma_op *op)
>  
>  		if (xe_svm_range_needs_migrate_to_vram(svm_range, vma, region)) {
>  			tile = &vm->xe->tiles[region_to_mem_type[region] - XE_PL_VRAM0];
> -			err = xe_svm_alloc_vram(vm, tile, svm_range, &ctx);
> +			err = xe_svm_alloc_vram(tile, svm_range, &ctx);
>  			if (err) {
>  				drm_dbg(&vm->xe->drm, "VRAM allocation failed, retry from userspace, asid=%u, gpusvm=%p, errno=%pe\n",
>  					vm->usm.asid, &vm->svm.gpusvm, ERR_PTR(err));
> -- 
> 2.49.0
> 


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