[PATCH 1/3] drm/xe/guc/ct: Improve g2h request handling during async gt reset

[Badal Nilawar <badal.nilawar@intel.com>]

It is possible that a g2h request may be cancelled while waiting for a
response due to an asynchronous gt reset. This commit ensures that in
such cases, caller will be notified by returning -ECANCELED.

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
---
 drivers/gpu/drm/xe/xe_guc_ct.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index c7673f56d413..b93b2821e4e8 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -512,6 +512,9 @@ void xe_guc_ct_stop(struct xe_guc_ct *ct)
 {
 	xe_guc_ct_set_state(ct, XE_GUC_CT_STATE_STOPPED);
 	stop_g2h_handler(ct);
+
+	/* Notify callers that CT stopped and G2H requests are cancelled */
+	wake_up_all(&ct->g2h_fence_wq);
 }
 
 static bool h2g_has_room(struct xe_guc_ct *ct, u32 cmd_len)
@@ -1018,6 +1021,19 @@ static int guc_ct_send_recv(struct xe_guc_ct *ct, const u32 *action, u32 len,
 
 	ret = wait_event_timeout(ct->g2h_fence_wq, g2h_fence.done, HZ);
 
+	/*
+	 * It is possible that the g2h request may be cancelled while waiting for a response due
+	 * to an asynchronous gt reset. In such cases, return -ECANCELED.
+	 */
+	mutex_lock(&ct->lock);
+	if (ct->state == XE_GUC_CT_STATE_STOPPED) {
+		xe_gt_dbg(gt, "H2G action %#x canceled as GT reset is in progress\n",
+			  action[0]);
+		mutex_unlock(&ct->lock);
+		return -ECANCELED;
+	}
+	mutex_unlock(&ct->lock);
+
 	/*
 	 * Ensure we serialize with completion side to prevent UAF with fence going out of scope on
 	 * the stack, since we have no clue if it will fire after the timeout before we can erase
-- 
2.34.1