Re: [V6 PATCH] Due to SLA agreement between PF and VFs, multi CCS mode can't be enabled when VFs are already enabled. Similarly, enabling VFs must be blocked when multi CCS mode enabled.

["Kumar G, Naresh" <naresh.kumar.g@intel.com>]

Hi All,

Please Discard this patch from reviewing as same patch being sent to the
mailing list to have intact review chain @
https://patchwork.freedesktop.org/patch/690313/?series=154538&rev=7

Thanks,
Naresh
On 25-11-2025 15:56, Nareshkumar Gollakoti wrote:
> v2:
> - function xe_device_is_vf_enabled has been refactored to
>    xe_sriov_pf_has_vfs_enabled and moved to xe_sriov_pf_helper.h.
> - The code now distinctly checks for SR-IOV VF mode and
>    SR-IOV PF with VFs enabled.
> - Log messages have been updated to explicitly state the current mode.
> - The function xe_multi_ccs_mode_enabled is moved to xe_device.h
> 
> v3: Described missed arg documentation for xe_sriov_pf_has_vfs_enabled
> 
> v4:
> - sysfs interface for CCS mode is not initialized
>    when operating in SRIOV VF Mode.
> - xe_sriov_pf_has_vfs_enabled() check is sufficient while CCS mode
>    enablement.
> - remove unnecessary comments as flow is self explanatory.
> 
> v5:(review comments from Michal)
> - Add xe device level CCS mode block with mutex lock and CCS mode state
> - necessesary functions to manage ccs mode state to provide strict mutual
>    exclusive support b/w CCS mode & SRIOV VF enabling
> 
> v6:
> - Re modeled implementation based on lockdown the PF using custom guard
>    supported functions by Michal
> 
> Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_gt_ccs_mode.c | 47 ++++++++++++++++++++++++-----
>   1 file changed, 39 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
> index 50fffc9ebf62..495bf517a6d3 100644
> --- a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
> +++ b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
> @@ -13,6 +13,7 @@
>   #include "xe_gt_sysfs.h"
>   #include "xe_mmio.h"
>   #include "xe_sriov.h"
> +#include "xe_sriov_pf_helpers.h"
>   
>   static void __xe_gt_apply_ccs_mode(struct xe_gt *gt, u32 num_engines)
>   {
> @@ -108,6 +109,30 @@ ccs_mode_show(struct device *kdev,
>   	return sysfs_emit(buf, "%u\n", gt->ccs_mode);
>   }
>   
> +static int xe_gt_prepare_ccs_mode_enabling(struct xe_device *xe,
> +					   struct xe_gt *gt)
> +{
> +	/*
> +	 * The arm guard is only activated during CCS mode enabling,
> +	 * and this shuould happen when CCS mode is in default mode.
> +	 * lockdown arm guard ensures there is no VFS enabling
> +	 * as CCS mode enabling in progress/enabled.
> +	 */
> +	if (!(gt->ccs_mode > 1))
> +		return xe_sriov_pf_arm_guard(xe, &xe->sriov.pf.guard_vfs_enabling,
> +					     true, NULL);
> +	return 0;
> +}
> +
> +static void xe_gt_finish_ccs_mode_enabling(struct xe_device *xe,
> +					   struct xe_gt *gt)
> +{
> +	/* disarm the guard, if CCS mode is reverted to default */
> +	if (!(gt->ccs_mode > 1))
> +		xe_sriov_pf_disarm_guard(xe, &xe->sriov.pf.guard_vfs_enabling,
> +					 true, NULL);
> +}
> +
>   static ssize_t
>   ccs_mode_store(struct device *kdev, struct device_attribute *attr,
>   	       const char *buff, size_t count)
> @@ -117,15 +142,13 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
>   	u32 num_engines, num_slices;
>   	int ret;
>   
> -	if (IS_SRIOV(xe)) {
> -		xe_gt_dbg(gt, "Can't change compute mode when running as %s\n",
> -			  xe_sriov_mode_to_string(xe_device_sriov_mode(xe)));
> -		return -EOPNOTSUPP;
> -	}
> +	ret = xe_gt_prepare_ccs_mode_enabling(xe, gt);
> +	if (ret)
> +		return ret;
>   
>   	ret = kstrtou32(buff, 0, &num_engines);
>   	if (ret)
> -		return ret;
> +		goto err;
>   
>   	/*
>   	 * Ensure number of engines specified is valid and there is an
> @@ -135,7 +158,8 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
>   	if (!num_engines || num_engines > num_slices || num_slices % num_engines) {
>   		xe_gt_dbg(gt, "Invalid compute config, %d engines %d slices\n",
>   			  num_engines, num_slices);
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto err;
>   	}
>   
>   	/* CCS mode can only be updated when there are no drm clients */
> @@ -143,7 +167,8 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
>   	if (!list_empty(&xe->drm.filelist)) {
>   		mutex_unlock(&xe->drm.filelist_mutex);
>   		xe_gt_dbg(gt, "Rejecting compute mode change as there are active drm clients\n");
> -		return -EBUSY;
> +		ret = -EBUSY;
> +		goto err;
>   	}
>   
>   	if (gt->ccs_mode != num_engines) {
> @@ -155,7 +180,13 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
>   
>   	mutex_unlock(&xe->drm.filelist_mutex);
>   
> +	xe_gt_finish_ccs_mode_enabling(xe, gt);
> +
>   	return count;
> +err:
> +	xe_gt_finish_ccs_mode_enabling(xe, gt);
> +
> +	return ret;
>   }
>   
>   static DEVICE_ATTR_RW(ccs_mode);