Re: [PATCH 2/3] drm/xe/pf: Use migration-friendly doorbells auto-provisioning

["Piotr Piórkowski" <piotr.piorkowski@intel.com>]

Michal Wajdeczko <michal.wajdeczko@intel.com> wrote on śro [2025-lis-05 19:32:51 +0100]:
> Instead of trying very hard to find the largest fair number of GuC
> doorbell IDs that could be allocated for VFs on the current GT, pick
> some smaller rounded down to power-of-two value that is more likely
> to be provisioned in the same manner by the other PF instance:
> 
>   num VFs | num doorbells
>   --------+--------------
>    63..32 | 4
>    31..16 | 8
>    15..8  | 16
>     7..4  | 32
>     3..2  | 64
>        1  | 128 (regular PF)
>        1  | 240 (admin only PF)
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c | 17 +++++++++++++++++
>  1 file changed, 17 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 14feda215d5b..701889e5dded 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_config.c
> @@ -1249,6 +1249,17 @@ int xe_gt_sriov_pf_config_bulk_set_dbs(struct xe_gt *gt, unsigned int vfid,
>  					   "GuC doorbell IDs", no_unit, n, err);
>  }
>  
> +static u32 pf_profile_fair_dbs(struct xe_gt *gt, unsigned int num_vfs)
> +{
> +	bool admin_only_pf = xe_sriov_pf_admin_only(gt_to_xe(gt));
> +
> +	/* XXX: preliminary */
> +	if (admin_only_pf && num_vfs == 1)
> +		return GUC_NUM_DOORBELLS - SZ_16;
> +
> +	return rounddown_pow_of_two(GUC_NUM_DOORBELLS / (num_vfs + 1));
> +}
> +
>  static u32 pf_estimate_fair_dbs(struct xe_gt *gt, unsigned int num_vfs)
>  {
>  	struct xe_guc_db_mgr *dbm = &gt->uc.guc.dbm;
> @@ -1281,6 +1292,7 @@ static u32 pf_estimate_fair_dbs(struct xe_gt *gt, unsigned int num_vfs)
>  int xe_gt_sriov_pf_config_set_fair_dbs(struct xe_gt *gt, unsigned int vfid,
>  				       unsigned int num_vfs)
>  {
> +	u32 profile = pf_profile_fair_dbs(gt, num_vfs);
>  	u32 fair;
>  
>  	xe_gt_assert(gt, vfid);
> @@ -1293,6 +1305,11 @@ int xe_gt_sriov_pf_config_set_fair_dbs(struct xe_gt *gt, unsigned int vfid,
>  	if (!fair)
>  		return -ENOSPC;
>  
> +	fair = min(fair, profile);
> +	if (fair < profile)
> +		xe_gt_sriov_info(gt, "Using non-profile provisioning (%s %u vs %u)\n",
> +				 "GuC doorbell IDs", fair, profile);
> +
>  	return xe_gt_sriov_pf_config_bulk_set_dbs(gt, vfid, num_vfs, fair);
>  }

LGTM:
Reviewed-by: Piotr Piórkowski <piotr.piorkowski@intel.com>

>  
> -- 
> 2.47.1
> 

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