Re: [PATCH 10/14] drm/xe/pf: Allow change PF scheduling priority using sysfs

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Mon, Oct 20, 2025 at 08:24:10PM +0200, Michal Wajdeczko wrote:
> We have just added bulk change of the scheduling priority for all
> VFs and PF, but that only allow to select LOW and NORMAL priority.
> 
> Add read-write attribute under PF to allow changing its priority
> without impacting other VFs priority settings.
> 
> For completeness also add read-only attributes under VFs, to show
> currently selected priority levels used by the VFs.
> 
>   /sys/bus/pci/drivers/xe/BDF/
>   ├── sriov_admin/
>       ├── pf/
>       │   └── profile
>       │       └── sched_priority	[RW] low, normal, high
>       ├── vf1/
>       │   └── profile
>       │       └── sched_priority	[RO] low, normal
> 

Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

> Writing "high" to the PF read-write attribute will change PF
> priority on all tiles/GTs to HIGH (schedule function in the next
> time-slice after current one completes and it has work). Writing
> "low" or "normal" to change priority to LOW/NORMAL is supported.
> 
> When read, those files will display the current and available
> scheduling priorities. The currently active priority level will
> be enclosed in square brackets, default output will be like:
> 
>  $ grep . -h sriov_admin/{pf,vf1,vf2}/profile/sched_priority
>  [low] normal high
>  [low] normal
>  [low] normal
> 
> Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Cc: Lucas De Marchi <lucas.demarchi@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_sriov_pf_sysfs.c | 82 +++++++++++++++++++++++++-
>  1 file changed, 80 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_sysfs.c b/drivers/gpu/drm/xe/xe_sriov_pf_sysfs.c
> index 26ba9a2efec9..a6be3c88fa4f 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_pf_sysfs.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_pf_sysfs.c
> @@ -17,6 +17,21 @@
>  #include "xe_sriov_pf_sysfs.h"
>  #include "xe_sriov_printk.h"
>  
> +static int emit_choice(char *buf, int choice, const char * const *array, size_t size)
> +{
> +	int pos = 0;
> +	int n;
> +
> +	for (n = 0; n < size; n++) {
> +		pos += sysfs_emit_at(buf, pos, "%s%s%s%s",
> +				    n ? " " : "",
> +				    n == choice ? "[" : "",
> +				    array[n],
> +				    n == choice ? "]" : "");
> +	}
> +	return pos + sysfs_emit_at(buf, pos, "\n");
> +}
> +
>  /*
>   * /sys/bus/pci/drivers/xe/BDF/
>   * :
> @@ -30,12 +45,14 @@
>   *     │   ├── ...
>   *     │   └── profile
>   *     │       ├── exec_quantum_ms
> - *     │       └── preempt_timeout_us
> + *     │       ├── preempt_timeout_us
> + *     │       └── sched_priority
>   *     ├── vf1/
>   *     │   ├── ...
>   *     │   └── profile
>   *     │       ├── exec_quantum_ms
> - *     │       └── preempt_timeout_us
> + *     │       ├── preempt_timeout_us
> + *     │       └── sched_priority
>   *     ├── vf2/
>   *     :
>   *     └── vfN/
> @@ -115,6 +132,12 @@ static const char * const sched_priority_names[] = {
>  	[GUC_SCHED_PRIORITY_HIGH] = "high",
>  };
>  
> +static bool sched_priority_change_allowed(unsigned int vfid)
> +{
> +	/* As of today GuC FW allows to selectively change only the PF priority. */
> +	return vfid == PFID;
> +}
> +
>  static bool sched_priority_high_allowed(unsigned int vfid)
>  {
>  	/* As of today GuC FW allows to select 'high' priority only for the PF. */
> @@ -199,15 +222,70 @@ static XE_SRIOV_VF_ATTR(NAME)
>  DEFINE_SIMPLE_PROVISIONING_SRIOV_VF_ATTR(exec_quantum_ms, eq, u32, "%u\n");
>  DEFINE_SIMPLE_PROVISIONING_SRIOV_VF_ATTR(preempt_timeout_us, pt, u32, "%u\n");
>  
> +static ssize_t xe_sriov_vf_attr_sched_priority_show(struct xe_device *xe, unsigned int vfid,
> +						    char *buf)
> +{
> +	size_t num_priorities = ARRAY_SIZE(sched_priority_names);
> +	u32 priority;
> +	int err;
> +
> +	err = xe_sriov_pf_provision_query_vf_priority(xe, vfid, &priority);
> +	if (err)
> +		return err;
> +
> +	if (!sched_priority_high_allowed(vfid))
> +		num_priorities--;
> +
> +	xe_assert(xe, priority < num_priorities);
> +	return emit_choice(buf, priority, sched_priority_names, num_priorities);
> +}
> +
> +static ssize_t xe_sriov_vf_attr_sched_priority_store(struct xe_device *xe, unsigned int vfid,
> +						     const char *buf, size_t count)
> +{
> +	size_t num_priorities = ARRAY_SIZE(sched_priority_names);
> +	int match;
> +	int err;
> +
> +	if (!sched_priority_change_allowed(vfid))
> +		return -EOPNOTSUPP;
> +
> +	if (!sched_priority_high_allowed(vfid))
> +		num_priorities--;
> +
> +	match = __sysfs_match_string(sched_priority_names, num_priorities, buf);
> +	if (match < 0)
> +		return -EINVAL;
> +
> +	err = xe_sriov_pf_provision_apply_vf_priority(xe, vfid, match);
> +	return err ?: count;
> +}
> +
> +static XE_SRIOV_VF_ATTR(sched_priority);
> +
>  static struct attribute *profile_vf_attrs[] = {
>  	&xe_sriov_vf_attr_exec_quantum_ms.attr,
>  	&xe_sriov_vf_attr_preempt_timeout_us.attr,
> +	&xe_sriov_vf_attr_sched_priority.attr,
>  	NULL
>  };
>  
> +static umode_t profile_vf_attr_is_visible(struct kobject *kobj,
> +					  struct attribute *attr, int index)
> +{
> +	struct xe_sriov_kobj *vkobj = to_xe_sriov_kobj(kobj);
> +
> +	if (attr == &xe_sriov_vf_attr_sched_priority.attr &&
> +	    !sched_priority_change_allowed(vkobj->vfid))
> +		return attr->mode & 0444;
> +
> +	return attr->mode;
> +}
> +
>  static const struct attribute_group profile_vf_attr_group = {
>  	.name = "profile",
>  	.attrs = profile_vf_attrs,
> +	.is_visible = profile_vf_attr_is_visible,
>  };
>  
>  static const struct attribute_group *xe_sriov_vf_attr_groups[] = {
> -- 
> 2.47.1
>