FAILED: patch "[PATCH] x86/locking: Use sfence for wmb() if SSE is available" failed to apply to 6.6-stable tree

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x d824ed1307680dd482f607b0e707c575f70668c4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090322-entrap-donation-7004@gregkh' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From d824ed1307680dd482f607b0e707c575f70668c4 Mon Sep 17 00:00:00 2001
From: Yao Zi <[email protected]>
Date: Sat, 1 Aug 2026 18:29:53 +0000
Subject: [PATCH] x86/locking: Use sfence for wmb() if SSE is available

When adding cc clobber to wmb()'s definition, the alternative() condition to use sfence was incorrectly raised from X86_FEATURE_XMM to X86_FEATURE_XMM2.

Restore the correct constraint for potential better performance on machines without SSE2.

index db70832232d4..3e78bb76153c 100644
@@ -17,7 +17,7 @@
 #define rmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "lfence", \
 				       X86_FEATURE_XMM2) ::: "memory", "cc")
 #define wmb() asm volatile(ALTERNATIVE("lock addl $0,-4(%%esp)", "sfence", \
-				       X86_FEATURE_XMM2) ::: "memory", "cc")
+				       X86_FEATURE_XMM) ::: "memory", "cc")
 #else
 #define __mb()	asm volatile("mfence":::"memory")
 #define __rmb()	asm volatile("lfence":::"memory")

From: Yao Zi <[email protected]>

[ Upstream commit d824ed1307680dd482f607b0e707c575f70668c4 ]

When adding cc clobber to wmb()'s definition, the alternative() condition to use sfence was incorrectly raised from X86_FEATURE_XMM to X86_FEATURE_XMM2.

Restore the correct constraint for potential better performance on machines without SSE2.

---
 arch/x86/include/asm/barrier.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index d0795b5fab46a..fc85b3df0f0fb 100644
@@ -17,7 +17,7 @@
 #define rmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "lfence", \
 				       X86_FEATURE_XMM2) ::: "memory", "cc")
 #define wmb() asm volatile(ALTERNATIVE("lock; addl $0,-4(%%esp)", "sfence", \
-				       X86_FEATURE_XMM2) ::: "memory", "cc")
+				       X86_FEATURE_XMM) ::: "memory", "cc")
 #else
 #define __mb()	asm volatile("mfence":::"memory")
 #define __rmb()	asm volatile("lfence":::"memory")

2.53.0