Re: [PATCH] drm/xe/pf: Reset PF scheduling defaults on auto provisioning restore

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] drm/xe/pf: missing master mutex around
  pf_reprovision_default() call
--

commit 5801d3ddee06076e86b0973d473b023b281cd2d2
Author: Rachapalli Bandi Jagadeesh <jagadeesh.rachapalli.bandi@intel.com>

drm/xe/pf: Reset PF scheduling defaults on auto provisioning restore

This commit resets PF scheduling defaults via pf_reprovision_default()
when restoring XE_SRIOV_PROVISIONING_MODE_AUTO in
xe_sriov_pf_provision_set_mode().

> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_provision.c b/drivers/gpu/drm/xe/xe_sriov_pf_provision.c
> index c37e422b5a5cd..6b338f8930753 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_provision.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_provision.c
> @@ -170,12 +170,18 @@ int xe_sriov_pf_provision_set_mode(struct xe_device *xe, enum xe_sriov_provision
>  		return 0;
>  
>  	if (mode == XE_SRIOV_PROVISIONING_MODE_AUTO) {
> +		int err;
>  		if (xe_sriov_pf_num_vfs(xe)) {
>  			xe_sriov_dbg(xe, "can't restore %s: VFs must be disabled!\n",
>  				     mode_to_string(mode));
>  			return -EBUSY;
>  		}
>  		pf_unprovision_all_vfs(xe);
> +
> +		/* custom PF EQ/PT/sched_if_idle would block fair VF scheduling */
> +		err = pf_reprovision_default(xe);
> +		if (err)
> +			return err;
>  	}

[Severity: Medium]
Does calling pf_reprovision_default() here without holding
xe_sriov_pf_master_mutex(xe) trigger a lockdep warning and update PF
scheduling state and GuC KLVs without synchronization?

pf_reprovision_default() and the *_locked() helpers it invokes require
xe_sriov_pf_master_mutex(xe):

drivers/gpu/drm/xe/xe_sriov_pf_provision.c:pf_reprovision_default() {
	...
	lockdep_assert_held(xe_sriov_pf_master_mutex(xe));

	for_each_gt(gt, xe, id) {
		err = xe_gt_sriov_pf_policy_set_sched_if_idle_locked(gt, false);
	...
}

However, the debugfs caller path (restore_auto_provisioning_write() ->
xe_sriov_pf_restore_auto_provisioning() ->
xe_sriov_pf_provision_set_mode()) does not acquire
xe_sriov_pf_master_mutex(xe), and pf_unprovision_all_vfs() only takes
and releases the mutex internally per VF.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110162609.41234-1-jagadeesh.rachapalli.bandi@intel.com?part=1