Re: [PATCH v4 29/34] drm/xe/vf: Workaround for race condition in GuC firmware during VF pause

["Lis, Tomasz" <tomasz.lis@intel.com>]

On 10/2/2025 7:53 AM, Matthew Brost wrote:
> A race condition exists where a paused VF's H2G request can be processed
> and subsequently rejected. This rejection results in a FAST_REQ failure
> being delivered to the KMD, which then terminates the CT via a dead
> worker and triggers a GT reset—an undesirable outcome.
>
> This workaround mitigates the issue by checking if a VF post-migration
> recovery is in progress and aborting these adverse actions accordingly.
> The GuC firmware will address this bug in an upcoming release. Once that
> version is available and VF migration depends on it, this workaround can
> be safely removed.
Reviewed-by: Tomasz Lis <tomasz.lis@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/xe/xe_guc_ct.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index 92822d131612..6673576b096b 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -1395,6 +1395,10 @@ static int parse_g2h_response(struct xe_guc_ct *ct, u32 *msg, u32 len)
>   
>   		fast_req_report(ct, fence);
>   
> +		/* FIXME: W/A race in the GuC, will get in firmware soon */
> +		if (xe_gt_recovery_inprogress(gt))
> +			return 0;
> +
>   		CT_DEAD(ct, NULL, PARSE_G2H_RESPONSE);
>   
>   		return -EPROTO;