Re: [PATCH 08/12] drm/xe: Introduce xe_ggtt_largest_hole

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 11.07.2024 19:11, Rodrigo Vivi wrote:
> Introduce a new xe_ggtt_largest_hole helper that attends the SRIOV
> demand and continue with the goal of limiting drm_mm access to xe_ggtt.
> 
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_ggtt.c               | 35 ++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_ggtt.h               |  1 +
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 23 ++------------
>  3 files changed, 38 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> index 67337bfeb81e..dbaf1ce87fb4 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.c
> +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> @@ -584,6 +584,41 @@ void xe_ggtt_remove_bo(struct xe_ggtt *ggtt, struct xe_bo *bo)
>  			    bo->flags & XE_BO_FLAG_GGTT_INVALIDATE);
>  }
>  
> +/**
> + * xe_ggtt_largest_hole - Largest GGTT hole
> + * @ggtt: the &xe_ggtt that will be inspected
> + * @alignment: mininum alignment

typo: minimum

> + * @spare: If not NULL: in: desired memory size to be spared / out: Adjusted possible spare
> + *
> + * Return: size of the largest continuous GGTT region
> + */
> +u64 xe_ggtt_largest_hole(struct xe_ggtt *ggtt, u64 alignment, u64 *spare)
> +{
> +	const struct drm_mm *mm = &ggtt->mm;
> +	const struct drm_mm_node *entry;
> +	u64 hole_min_start = xe_wopcm_size(tile_to_xe(ggtt->tile));

this is likely not needed any more as xe_ggtt is always above WOPCM
(unlikely to previous driver ;)

> +	u64 hole_start, hole_end, hole_size;
> +	u64 max_hole = 0;
> +
> +	mutex_lock(&ggtt->lock);
> +
> +	drm_mm_for_each_hole(entry, mm, hole_start, hole_end) {
> +		hole_start = max(hole_start, hole_min_start);
> +		hole_start = ALIGN(hole_start, alignment);
> +		hole_end = ALIGN_DOWN(hole_end, alignment);
> +		if (hole_start >= hole_end)
> +			continue;
> +		hole_size = hole_end - hole_start;
> +		if (spare)
> +			*spare -= min3(*spare, hole_size, max_hole);
> +		max_hole = max(max_hole, hole_size);
> +	}
> +
> +	mutex_unlock(&ggtt->lock);
> +
> +	return max_hole;
> +}
> +
>  #ifdef CONFIG_PCI_IOV
>  static u64 xe_encode_vfid_pte(u16 vfid)
>  {
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.h b/drivers/gpu/drm/xe/xe_ggtt.h
> index f816b3c0732b..31060fe7644b 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.h
> +++ b/drivers/gpu/drm/xe/xe_ggtt.h
> @@ -29,6 +29,7 @@ int xe_ggtt_insert_bo(struct xe_ggtt *ggtt, struct xe_bo *bo);
>  int xe_ggtt_insert_bo_at(struct xe_ggtt *ggtt, struct xe_bo *bo,
>  			 u64 start, u64 end);
>  void xe_ggtt_remove_bo(struct xe_ggtt *ggtt, struct xe_bo *bo);
> +u64 xe_ggtt_largest_hole(struct xe_ggtt *ggtt, u64 alignment, u64 *spare);
>  
>  int xe_ggtt_dump(struct xe_ggtt *ggtt, struct drm_printer *p);
>  
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> index efaf188290ea..1d17c34fe5a4 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> @@ -590,30 +590,11 @@ int xe_gt_sriov_pf_config_bulk_set_ggtt(struct xe_gt *gt, unsigned int vfid,
>  static u64 pf_get_max_ggtt(struct xe_gt *gt)
>  {
>  	struct xe_ggtt *ggtt = gt_to_tile(gt)->mem.ggtt;
> -	const struct drm_mm *mm = &ggtt->mm;
> -	const struct drm_mm_node *entry;
>  	u64 alignment = pf_get_ggtt_alignment(gt);
>  	u64 spare = pf_get_spare_ggtt(gt);
> -	u64 hole_min_start = xe_wopcm_size(gt_to_xe(gt));
> -	u64 hole_start, hole_end, hole_size;
> -	u64 max_hole = 0;
> -
> -	mutex_lock(&ggtt->lock);
> -
> -	drm_mm_for_each_hole(entry, mm, hole_start, hole_end) {
> -		hole_start = max(hole_start, hole_min_start);
> -		hole_start = ALIGN(hole_start, alignment);
> -		hole_end = ALIGN_DOWN(hole_end, alignment);
> -		if (hole_start >= hole_end)
> -			continue;
> -		hole_size = hole_end - hole_start;
> -		xe_gt_sriov_dbg_verbose(gt, "HOLE start %llx size %lluK\n",
> -					hole_start, hole_size / SZ_1K);
> -		spare -= min3(spare, hole_size, max_hole);
> -		max_hole = max(max_hole, hole_size);
> -	}
> +	u64 max_hole;
>  
> -	mutex_unlock(&ggtt->lock);
> +	max_hole = xe_ggtt_largest_hole(ggtt, alignment, &spare);
>  
>  	xe_gt_sriov_dbg_verbose(gt, "HOLE max %lluK reserved %lluK\n",
>  				max_hole / SZ_1K, spare / SZ_1K);