Re: [PATCH v3 3/5] drm/xe/vf: Skip fixups on VF migration before getting GGTT info

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

On 10/16/2025 2:05 PM, Tomasz Lis wrote:
> The GuC RESFIX state should be achievable only after a successful
> handshake. If VF KMD has no GGTT configuration yet and we still got
> into RESFIX state, then either we're dealing with unclean initial
> state due to unusual actions before probe, or the migration
> happened while xe init (started by probe) was running.
> 
> In 1st case (VF migration before probe), we should just skip migration.
> Init procedure will ensure exit from RESFIX state as it starts GuC
> handshake with a reset.
> 
> In 2nd case (VF migration during xe init), the migration procedure
> should execute normally if GGTT configuration was already acquired
> from GuC, and can be skipped if it was not acquired.

we initiate recovery as part of the MEMIRQ handling

but to get MEMIRQ interrupt from the GuC we need to setup it first
to setup MEMIRQ vector we need to obtain GGTT data from GuC
only the we can register this MEMIRQ vector in GuC

so valid GGTT data seems to be hard prerequisite for this scenario

thus vf_ggtt_queried() should be always true, no?

> 
> This solution will avoid crashes due to the VF migration running
> on non-initialized xe sub-structures. But it is not enough to allow
> fully reliable migration during driver probe. In particular, the
> situation where the probe might not end successfully, is:
> 
> * The VF is paused and migrated after GuC reset (vf_bootstrap) but
> before config is acquired (vf_query_config). In such case, GuC may
> remain in RESFIX state, leading to timeouting requests.
> 
> Signed-off-by: Tomasz Lis <tomasz.lis@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_vf.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> index 34c68de6e2f3..bb0b71a47125 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> @@ -1149,6 +1149,12 @@ void xe_gt_sriov_vf_print_version(struct xe_gt *gt, struct drm_printer *p)
>  		   pf_version->major, pf_version->minor);
>  }
>  
> +static bool vf_ggtt_queried(struct xe_tile *tile)
> +{
> +	guard(mutex)(&tile->mem.ggtt->lock);
> +	return xe_tile_sriov_vf_ggtt(tile) != 0;
> +}
> +
>  static bool vf_post_migration_shutdown(struct xe_gt *gt)
>  {
>  	struct xe_device *xe = gt_to_xe(gt);
> @@ -1260,6 +1266,11 @@ static void vf_post_migration_recovery(struct xe_gt *gt)
>  	xe_gt_sriov_dbg(gt, "migration recovery in progress\n");
>  
>  	xe_pm_runtime_get(xe);
> +
> +	/* If during init and before GGTT configuration, skip the procedure. */
> +	if (!vf_ggtt_queried(gt_to_tile(gt)))
> +		goto skip;
> +
>  	retry = vf_post_migration_shutdown(gt);
>  	if (retry)
>  		goto queue;
> @@ -1282,6 +1293,7 @@ static void vf_post_migration_recovery(struct xe_gt *gt)
>  
>  	vf_post_migration_kickstart(gt);
>  
> +skip:
>  	xe_pm_runtime_put(xe);
>  	xe_gt_sriov_notice(gt, "migration recovery ended\n");
>  	return;