Re: [PATCH v5 16/20] drm/xe/svm: Add xe_svm_range_validate_and_evict() function

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Apr 29, 2025 at 04:12:29PM +0530, Himal Prasad Ghimiray wrote:
> The xe_svm_range_validate_and_evict() function checks if a range is
> valid and located in the desired memory region. Additionally, if the
> range is valid in VRAM but the desired region is SMEM, it evicts the
> ranges to SMEM.
> 
> v2
> - Fix function stub in xe_svm.h
> - Fix doc
> 
> v3 (Matthew Brost)
> - Remove extra new line
> - s/range->base.flags.has_devmem_pages/xe_svm_range_in_vram
> 
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_svm.c | 37 +++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_svm.h | 12 ++++++++++++
>  2 files changed, 49 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
> index 90fae13b77ae..55c5373b7989 100644
> --- a/drivers/gpu/drm/xe/xe_svm.c
> +++ b/drivers/gpu/drm/xe/xe_svm.c
> @@ -637,6 +637,43 @@ static bool xe_svm_range_is_valid(struct xe_svm_range *range,
>  		&& (!devmem_only || range->base.flags.migrate_devmem);
>  }
>  
> +/**
> + * xe_svm_range_validate_and_evict() - Check if the SVM range is valid
> + * @vm: xe_vm pointer
> + * @range: Pointer to the SVM range structure
> + * @tile_mask: Mask representing the tiles to be checked
> + * @devmem_only: if true range needs to be in devmem
> + *
> + * The xe_svm_range_validate_and_evict() function checks if a range is
> + * valid and located in the desired memory region. Additionally, if the
> + * range is valid in VRAM but the desired region is SMEM, it evicts the
> + * ranges to SMEM.
> + *
> + * Return: true if the range is valid, false otherwise
> + */
> +bool xe_svm_range_validate_and_evict(struct xe_vm *vm,
> +				     struct xe_svm_range *range,
> +				     u8 tile_mask, bool devmem_only)

s/devmem_only/devmem_preferred

> +{
> +	bool range_evict = false;
> +	bool ret;
> +
> +	xe_svm_notifier_lock(vm);
> +
> +	ret = (range->tile_present & ~range->tile_invalidated & tile_mask) == tile_mask &&
> +	       (devmem_only == xe_svm_range_in_vram(range));
> +
> +	if (!ret && !devmem_only && xe_svm_range_in_vram(range))
> +		range_evict = true;
> +
> +	xe_svm_notifier_unlock(vm);
> +
> +	if (range_evict)
> +		drm_gpusvm_range_evict(&vm->svm.gpusvm, &range->base);

Sorry missed this eariler. I think this step should be left to latter in
the software pipeline - e.g., In prefetch_ranges in the following patch.

Migration are costly and this is the step we'd want to thread for
performancd. So if some migrations are done in vm_bind_ioctl_ops_create
and other in prefetch_ranges it would make the threading logic tricky
comapred all migrations being done in prefetch_ranges.

Matt

> +
> +	return ret;
> +}
> +
>  #if IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR)
>  static struct xe_vram_region *tile_to_vr(struct xe_tile *tile)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_svm.h b/drivers/gpu/drm/xe/xe_svm.h
> index 9be7bb25725c..e6f71ad0b17b 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -83,6 +83,10 @@ int xe_svm_range_get_pages(struct xe_vm *vm, struct xe_svm_range *range,
>  bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range, struct xe_vma *vma,
>  					bool preferred_region_is_vram);
>  
> +bool xe_svm_range_validate_and_evict(struct xe_vm *vm,
> +				     struct xe_svm_range *range,
> +				     u8 tile_mask, bool devmem_only);
> +
>  /**
>   * xe_svm_range_has_dma_mapping() - SVM range has DMA mapping
>   * @range: SVM range
> @@ -276,6 +280,14 @@ bool xe_svm_range_needs_migrate_to_vram(struct xe_svm_range *range, struct xe_vm
>  	return false;
>  }
>  
> +static inline
> +bool xe_svm_range_validate_and_evict(struct xe_vm *vm,
> +				     struct xe_svm_range *range,
> +				     u8 tile_mask, bool devmem_only)
> +{
> +	return false;
> +}
> +
>  #define xe_svm_assert_in_notifier(...) do {} while (0)
>  #define xe_svm_range_has_dma_mapping(...) false
>  
> -- 
> 2.34.1
>