From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6CA942D0C79 for ; Sun, 1 Mar 2026 01:36:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772328964; cv=none; b=njyiSqt7y2s2cbpFAD2qr3fNwXFBvtO7EoNtqo8aoSc+7C3fu0oDvZDUtHfVGt8tm+nuWnBQ1Y1ncJ2AnkHg3pZBjwsyQk8OdA6MCJ0+0lTrCxv99hpkUFafl4MRsYo4HrmBMjIhVIMRriX6vsa8k2rguQywsazZENHBjnSm2Bs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772328964; c=relaxed/simple; bh=o8QrnyXx5YcxW+HWTjGYCHtVrysbfGeXpzhFdGiZZJw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=pmljeROMFdt0UYUz/ODaA8F+L3jiHNX/kRLd2hxcP4CB5WUzPygmfYMVuyWeOM3D7tMVbv0AgJdvxjQtVW9hTYd9ExWyNuQ73AHn/yGGBuqjeyVJDmGx9h6B73yq/meUrv7Ss5fSKMUxX1RfpSg97CwfZdx7PAVkgfzoQhcPeaM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TmpEkmVL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TmpEkmVL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A6F77C19421; Sun, 1 Mar 2026 01:36:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772328964; bh=o8QrnyXx5YcxW+HWTjGYCHtVrysbfGeXpzhFdGiZZJw=; h=From:To:Cc:Subject:Date:From; b=TmpEkmVLeRX5EGm3U8/LrfQy6/1E31LEuzhH+2n6CnHLW6h947oah5JgdL1FPLQ1M BEHQL7b7pFouA6gI26X2LhppY8Bfu3BiteIh30JzLMhuObUr66kS9PHEVFd1itKbFS OIUhGbpcZ/ebf8pz/PoRkzEW3BL5Ag6lcGOtJO4UdBD2Yoqx7Ia4vTMBzloHN66H4j SqXCBO9Dk7cqbvbGbKzsZH4u5V2E0Cs2uM7MNwX6cGzet/mlP4hTHcbYrBS3d5Zelm vm9ehSs+fUfV/CP0Br5nsEi9TGbWrNjGa4px/AGgkjAcc7tZGZB1oYsikpUmHKF8zQ 99qg4QcYALGLQ== From: Sasha Levin To: stable@vger.kernel.org, elver@google.com Cc: Boqun Feng , David Laight , Will Deacon , linux-arm-kernel@lists.infradead.org Subject: FAILED: Patch "arm64: Fix non-atomic __READ_ONCE() with CONFIG_LTO=y" failed to apply to 6.6-stable tree Date: Sat, 28 Feb 2026 20:36:02 -0500 Message-ID: <20260301013602.1695886-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit 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 . Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From bb0c99e08ab9aa6d04b40cb63c72db9950d51749 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 30 Jan 2026 14:28:24 +0100 Subject: [PATCH] arm64: Fix non-atomic __READ_ONCE() with CONFIG_LTO=y The implementation of __READ_ONCE() under CONFIG_LTO=y incorrectly qualified the fallback "once" access for types larger than 8 bytes, which are not atomic but should still happen "once" and suppress common compiler optimizations. The cast `volatile typeof(__x)` applied the volatile qualifier to the pointer type itself rather than the pointee. This created a volatile pointer to a non-volatile type, which violated __READ_ONCE() semantics. Fix this by casting to `volatile typeof(*__x) *`. With a defconfig + LTO + debug options build, we see the following functions to be affected: xen_manage_runstate_time (884 -> 944 bytes) xen_steal_clock (248 -> 340 bytes) ^-- use __READ_ONCE() to load vcpu_runstate_info structs Fixes: e35123d83ee3 ("arm64: lto: Strengthen READ_ONCE() to acquire when CONFIG_LTO=y") Cc: stable@vger.kernel.org Reviewed-by: Boqun Feng Signed-off-by: Marco Elver Tested-by: David Laight Signed-off-by: Will Deacon --- arch/arm64/include/asm/rwonce.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/rwonce.h b/arch/arm64/include/asm/rwonce.h index 78beceec10cda..fc0fb42b0b641 100644 --- a/arch/arm64/include/asm/rwonce.h +++ b/arch/arm64/include/asm/rwonce.h @@ -58,7 +58,7 @@ default: \ atomic = 0; \ } \ - atomic ? (typeof(*__x))__u.__val : (*(volatile typeof(__x))__x);\ + atomic ? (typeof(*__x))__u.__val : (*(volatile typeof(*__x) *)__x);\ }) #endif /* !BUILD_VDSO */ -- 2.51.0