From: Jonathan Cavitt <jonathan.cavitt@intel.com>
Date: Mon, 22 Dec 2025 20:19:59 +0000 (+0000)
Subject: drm/xe/guc: READ/WRITE_ONCE g2h_fence->done
X-Git-Tag: v6.19-rc4~12^2~2^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bed2a6bd20681aacfb063015c1edfab6f58a333e;p=thirdparty%2Fkernel%2Fstable.git

drm/xe/guc: READ/WRITE_ONCE g2h_fence->done

Use READ_ONCE and WRITE_ONCE when operating on g2h_fence->done
to prevent the compiler from ignoring important modifications
to its value.

Fixes: dd08ebf6c352 ("drm/xe: Introduce a new DRM driver for Intel GPUs")
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20251222201957.63245-5-jonathan.cavitt@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
(cherry picked from commit b5179dbd1c14743ae80f0aaa28eaaf35c361608f)
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
---

diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
index 4ac434ad216f..a5019d1e741b 100644
--- a/drivers/gpu/drm/xe/xe_guc_ct.c
+++ b/drivers/gpu/drm/xe/xe_guc_ct.c
@@ -104,7 +104,9 @@ static void g2h_fence_cancel(struct g2h_fence *g2h_fence)
 {
 	g2h_fence->cancel = true;
 	g2h_fence->fail = true;
-	g2h_fence->done = true;
+
+	/* WRITE_ONCE pairs with READ_ONCEs in guc_ct_send_recv. */
+	WRITE_ONCE(g2h_fence->done, true);
 }
 
 static bool g2h_fence_needs_alloc(struct g2h_fence *g2h_fence)
@@ -1203,10 +1205,13 @@ retry_same_fence:
 		return ret;
 	}
 
-	ret = wait_event_timeout(ct->g2h_fence_wq, g2h_fence.done, HZ);
+	/* READ_ONCEs pairs with WRITE_ONCEs in parse_g2h_response
+	 * and g2h_fence_cancel.
+	 */
+	ret = wait_event_timeout(ct->g2h_fence_wq, READ_ONCE(g2h_fence.done), HZ);
 	if (!ret) {
 		LNL_FLUSH_WORK(&ct->g2h_worker);
-		if (g2h_fence.done) {
+		if (READ_ONCE(g2h_fence.done)) {
 			xe_gt_warn(gt, "G2H fence %u, action %04x, done\n",
 				   g2h_fence.seqno, action[0]);
 			ret = 1;
@@ -1454,7 +1459,8 @@ static int parse_g2h_response(struct xe_guc_ct *ct, u32 *msg, u32 len)
 
 	g2h_release_space(ct, GUC_CTB_HXG_MSG_MAX_LEN);
 
-	g2h_fence->done = true;
+	/* WRITE_ONCE pairs with READ_ONCEs in guc_ct_send_recv. */
+	WRITE_ONCE(g2h_fence->done, true);
 	smp_mb();
 
 	wake_up_all(&ct->g2h_fence_wq);