Re: [PATCH v3 1/5] drm/xe/vf: Helper for telling whether CCS migration BBs are needed

[Michal Wajdeczko <michal.wajdeczko@intel.com>]

On 10/16/2025 2:05 PM, Tomasz Lis wrote:
> To avoid having duplicated checks, and also provide clear
> documentation of what are we checking for, the conditions
> for initing CCS BBs for VF migration are closed into a function.

I would drop "BBs" from title and commit message, as this is
just an implementation detail of the "VF CCS migration" feature
that doesn't need to be exposed right now.

> 
> Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_sriov_vf_ccs.c | 15 ++++++++++++++-
>  drivers/gpu/drm/xe/xe_sriov_vf_ccs.h |  2 ++
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_sriov_vf_ccs.c b/drivers/gpu/drm/xe/xe_sriov_vf_ccs.c
> index 790249801364..7688d1baf42f 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_vf_ccs.c
> +++ b/drivers/gpu/drm/xe/xe_sriov_vf_ccs.c
> @@ -260,6 +260,19 @@ int xe_sriov_vf_ccs_register_context(struct xe_device *xe)
>  	return err;
>  }
>  
> +/**
> + * xe_sriov_vf_ccs_migration_bb_needed - Whether GuC requires CCS copy BBs for VF migration.

all functions in xe_sriov_vf_ccs.c are related to "migration"
but only this one mention it in its name, either rename other
functions to match this one, or name this one simply as:

      xe_sriov_vf_ccs_is_needed()

> + * @xe: the &xe_device instance.
> + *
> + * Only selected platforms require VF KMD to maintain CCS copy BBs and linked LRCAs.
> + *
> + * Return: true if the BBs are needed, false otherwise.

"true if VF driver must participate in the CCS migration"

> + */
> +bool xe_sriov_vf_ccs_migration_bb_needed(struct xe_device *xe)
> +{

this should be always called from VF code, so even if not strictly required:

	xe_assert(xe, IS_SRIOV(xe))

> +	return !IS_DGFX(xe) && xe_device_has_flat_ccs(xe);
> +}
> +
>  static void xe_sriov_vf_ccs_fini(void *arg)
>  {
>  	struct xe_sriov_vf_ccs_ctx *ctx = arg;
> @@ -294,7 +307,7 @@ int xe_sriov_vf_ccs_init(struct xe_device *xe)
>  	xe_assert(xe, IS_SRIOV_VF(xe));
>  	xe_assert(xe, xe_sriov_vf_migration_supported(xe));
>  
> -	if (IS_DGFX(xe) || !xe_device_has_flat_ccs(xe))
> +	if (!xe_sriov_vf_ccs_migration_bb_needed(xe))
>  		return 0;
>  
>  	for_each_ccs_rw_ctx(ctx_id) {
> diff --git a/drivers/gpu/drm/xe/xe_sriov_vf_ccs.h b/drivers/gpu/drm/xe/xe_sriov_vf_ccs.h
> index f8ca6efce9ee..dcba4173c712 100644
> --- a/drivers/gpu/drm/xe/xe_sriov_vf_ccs.h
> +++ b/drivers/gpu/drm/xe/xe_sriov_vf_ccs.h
> @@ -14,6 +14,8 @@ struct drm_printer;
>  struct xe_device;
>  struct xe_bo;
>  
> +bool xe_sriov_vf_ccs_migration_bb_needed(struct xe_device *xe);
> +
>  int xe_sriov_vf_ccs_init(struct xe_device *xe);
>  int xe_sriov_vf_ccs_attach_bo(struct xe_bo *bo);
>  int xe_sriov_vf_ccs_detach_bo(struct xe_bo *bo);