Re: [PATCH v4 3/5] drm/xe/pf: Add a helper function to get a VF's backing object in LMEM

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

On Mon, 2025-09-15 at 00:21 -0700, Vivek Kasireddy wrote:
> To properly import a dmabuf that is associated with a VF (or that
> originates in a Guest VM that includes a VF), we need to know where
> in LMEM the VF's allocated regions exist. Therefore, introduce a
> new helper to return the object that backs the VF's regions in LMEM.
> 
> v2:
> - Make the helper return the LMEM object instead of the start address
> 
> v3:
> - Move the declaration of the helper under other lmem helpers
> (Michal)

In XeKMD we're typically using VRAM instead of LMEM, IMO we should try
to be consistent with this.

> 
> Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 23
> ++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h |  1 +
>  2 files changed, 24 insertions(+)
> 
> 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 6344b5205c08..1bfcd35cc8ef 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> @@ -1535,6 +1535,29 @@ u64 xe_gt_sriov_pf_config_get_lmem(struct
> xe_gt *gt, unsigned int vfid)
>  	return size;
>  }
>  
> +/**
> + * xe_gt_sriov_pf_config_get_lmem_obj - Get VF's LMEM BO.
> + * @gt: the &xe_gt
> + * @vfid: the VF identifier
> + *
> + * This function can only be called on PF.
> + *
> + * Return: BO that is backing VF's quota in LMEM.
> + */
> +struct xe_bo *xe_gt_sriov_pf_config_get_lmem_obj(struct xe_gt *gt,
> +						 unsigned int vfid)
> +{
> +	struct xe_gt_sriov_config *config;
> +	struct xe_bo *lmem_obj;
> +
> +	mutex_lock(xe_gt_sriov_pf_master_mutex(gt));
> +	config = pf_pick_vf_config(gt, vfid);
> +	lmem_obj = config->lmem_obj;

Bump the reference count? I think Matt mentioned this as well?

> +	mutex_unlock(xe_gt_sriov_pf_master_mutex(gt));
> +
> +	return lmem_obj;
> +}
> +
>  /**
>   * xe_gt_sriov_pf_config_set_lmem - Provision VF with LMEM.
>   * @gt: the &xe_gt (can't be media)
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> index 513e6512a575..bbc5c238cbf6 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.h
> @@ -36,6 +36,7 @@ int xe_gt_sriov_pf_config_set_lmem(struct xe_gt
> *gt, unsigned int vfid, u64 size
>  int xe_gt_sriov_pf_config_set_fair_lmem(struct xe_gt *gt, unsigned
> int vfid, unsigned int num_vfs);
>  int xe_gt_sriov_pf_config_bulk_set_lmem(struct xe_gt *gt, unsigned
> int vfid, unsigned int num_vfs,
>  					u64 size);
> +struct xe_bo *xe_gt_sriov_pf_config_get_lmem_obj(struct xe_gt *gt,
> unsigned int vfid);
>  
>  u32 xe_gt_sriov_pf_config_get_exec_quantum(struct xe_gt *gt,
> unsigned int vfid);
>  int xe_gt_sriov_pf_config_set_exec_quantum(struct xe_gt *gt,
> unsigned int vfid, u32 exec_quantum);