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 0C32DFD0045 for ; Sun, 1 Mar 2026 01:53:17 +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=JvZDDrjts6+FFmsyaibX0+euslssgBEFvkB8H1lurwM=; b=4NEkur0OT9XyqyjR6TEkabgSM5 q/dL8b8SOjc8fyfpfaiev/lyA5Eu+280R6G2evBroC2Kc1XlydACFA7YubnGlMCeSz6ey+NMTrC0D zs0HP4tOEZAAS8+MTult1L7iWV9kzMuNP7Y7vgN5rO71xFwu6xZsh4ZKaxvzna2Ve/R9F6IBFfz4u d3BichT3Sn0gWRz6ShkPraUVhGOQWw/PQy3do1Sw6uRLAuXjw/D3W4DKt0hzvX3Q5HA6u/2wpoTyP 5jYBaSyCE8HY8J8AcZQ7tQHwO11Pkcb7OuPfUaQUwB9n4swEUzoWANS8gAOIDJ9mxDxhqb4YIrQQA g/ggAe7w==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vwVzd-0000000AgFx-1gFx; Sun, 01 Mar 2026 01:53:13 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vwVzc-0000000AgF8-0FeV for linux-arm-kernel@lists.infradead.org; Sun, 01 Mar 2026 01:53:12 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 80ECC6013A; Sun, 1 Mar 2026 01:53:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 88E35C19421; Sun, 1 Mar 2026 01:53:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772329991; bh=kxeBlUcPBFMnqFuMlYJuhCiq2X6vslJ1sOWPFc360pQ=; h=From:To:Cc:Subject:Date:From; b=GxRnl2kKTvymFxK6SoxdCdntLcyBEnI3mjU4F8gpJZlPQCpsFu+5WUgJsoweRX5Q6 nofjBYwPe0gxfwojsvQW6YqzRtEI7S9sjDepvOOlPI0O2CoIZB4qhZ9oXYd/2zdQ8h nGNOxE2gL33trs3DRq3HayTTdzSWnYF75X9kmfyeKKLNStAHot3lLRj3ijhCnnGY5q C8ko7n3SvCf70bI8f8l2FlDRBDSeYE6Wj2wk8jq2/k5qjWv8XV2hOZZXMMprMUg56n ntfWF4ust2tso3myXkvRRB+JyYwl72DGWuPZxjRPIkmH0GxJlLufptT5d0OkuYBeUS k0G4Rz5hSXPxw== 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 5.15-stable tree Date: Sat, 28 Feb 2026 20:53:09 -0500 Message-ID: <20260301015309.1719827-1-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-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 5.15-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