From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4298BFD0045 for ; Sun, 1 Mar 2026 01:36:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=OzOnvSf+c47GyCQjthM/O0b0Nbl1+cPX/Q1HbHy5Htw=; b=BYNwo0TqzL+zbh+z+L2YAn92mv HNXmcaBXvk+uIQVi5grUw0sAsoP/YgQsiusmytBJniW/DsEAdpKtMR+uJGnnKf0ziV4oSTHpD7Jku 3RyzoTT9PC249DTraH4J2QR/RJ0XPSr8RQt6dAC/07Fc/Afpm3zStt8uubVI8r9JYdUnHnZCAdCAP sE2qOVU7zFgoaMYA56JefBjeELl88R/r4HAy6jrYYIM4D8xLC3ipSplkBGJt4+lKSlemnN8l9fgNl 7tQrIm/Krw+YtUVmOlfjvI+BPnj9QvNOtCMBKUdNsz5LPq+84mVZhvMtbmTKGXBM4F9vqu/OLkTzO xfxj1fNA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vwVj4-0000000AaGY-49Fb; Sun, 01 Mar 2026 01:36:06 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vwVj2-0000000AaFD-413Z for linux-arm-kernel@lists.infradead.org; Sun, 01 Mar 2026 01:36:05 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 6FD5E40B7F; Sun, 1 Mar 2026 01:36:04 +0000 (UTC) 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 MIME-Version: 1.0 X-Patchwork-Hint: ignore X-stable: review Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260228_173605_011419_E071964C X-CRM114-Status: GOOD ( 15.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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