From patchwork Fri Mar 25 02:22:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Chang S. Bae" X-Patchwork-Id: 12791226 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91018C433F5 for ; Fri, 25 Mar 2022 02:30:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357728AbiCYCcK (ORCPT ); Thu, 24 Mar 2022 22:32:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51382 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357725AbiCYCcK (ORCPT ); Thu, 24 Mar 2022 22:32:10 -0400 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16BDFB715F; Thu, 24 Mar 2022 19:30:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1648175437; x=1679711437; h=from:to:cc:subject:date:message-id:in-reply-to: references; bh=PTNFCFzP7Qzi5GxtYWpCTaMvmu7DnLjllzpv1VI5L78=; b=dvUYMaKiNgtn6W/ia29VVjofGpV+T2IgPBrBvx1t1J9Cu0bjK2bUuv8M CLAhH5BcVkJVHNIZOQY8Tcs8yH92+XY0Q8QMo/T3YXVhTSuWDxJ2dmqhN rf0twNZ8FJqZTe8BK+4wciTu7fcbLtoScjWWpyI5XiPXqH4DyZC286l3H xT4hpeSD3O7KV2hv3/YM41fb/UJpuO+s4VFVwd8GqC3s2cJwt08xN/iRZ c2MrXQf1UK6KKc+1j1A7IofzKhisYOldM72HO5Lmr0PfRivVCub+LfK9m 8zOBIXZ6WJGfmmHc0Yyft8L94+otYk5CUxQYMyJ3DQnlx9+qbHfJtDuhj A==; X-IronPort-AV: E=McAfee;i="6200,9189,10296"; a="321733682" X-IronPort-AV: E=Sophos;i="5.90,209,1643702400"; d="scan'208";a="321733682" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Mar 2022 19:30:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,209,1643702400"; d="scan'208";a="693531279" Received: from chang-linux-3.sc.intel.com ([172.25.112.114]) by fmsmga001.fm.intel.com with ESMTP; 24 Mar 2022 19:30:35 -0700 From: "Chang S. Bae" To: linux-kernel@vger.kernel.org, x86@kernel.org, linux-pm@vger.kernel.org Cc: tglx@linutronix.de, dave.hansen@linux.intel.com, peterz@infradead.org, bp@alien8.de, rafael@kernel.org, ravi.v.shankar@intel.com, chang.seok.bae@intel.com Subject: [PATCH v3 1/3] x86/fpu: Make XCR0 accessors immune to unwanted compiler reordering Date: Thu, 24 Mar 2022 19:22:17 -0700 Message-Id: <20220325022219.829-2-chang.seok.bae@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20220325022219.829-1-chang.seok.bae@intel.com> References: <20220325022219.829-1-chang.seok.bae@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Some old GCC versions (4.9.x and 5.x) have an issue that incorrectly reordering volatile asm statements with each other [1]. While this bug was fixed on later versions (8.1, 7.3, and 6.5), and the kernel's current XCR0 read/write do not appear to be impacted, it is preventive to ensure them on the program order. Have a memory clobber for write to prevent caching/reordering memory accesses across other XCR0 writes. A dummy operand with an arbitrary address can prevent the compiler from reordering with other writes. Add the dummy operand for read as used for other accessors in aa5cacdc29d ("x86/asm: Replace __force_order with a memory clobber"). [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82602 Signed-off-by: Chang S. Bae Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v2: * Add as a new patch (Dave Hansen). --- arch/x86/include/asm/fpu/xcr.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/fpu/xcr.h b/arch/x86/include/asm/fpu/xcr.h index 9656a5bc6fea..9b513e7c0161 100644 --- a/arch/x86/include/asm/fpu/xcr.h +++ b/arch/x86/include/asm/fpu/xcr.h @@ -2,6 +2,8 @@ #ifndef _ASM_X86_FPU_XCR_H #define _ASM_X86_FPU_XCR_H +#include + #define XCR_XFEATURE_ENABLED_MASK 0x00000000 #define XCR_XFEATURE_IN_USE_MASK 0x00000001 @@ -9,7 +11,8 @@ static inline u64 xgetbv(u32 index) { u32 eax, edx; - asm volatile("xgetbv" : "=a" (eax), "=d" (edx) : "c" (index)); + asm volatile("xgetbv" : "=a" (eax), "=d" (edx) : "c" (index), + __FORCE_ORDER); return eax + ((u64)edx << 32); } @@ -18,7 +21,8 @@ static inline void xsetbv(u32 index, u64 value) u32 eax = value; u32 edx = value >> 32; - asm volatile("xsetbv" :: "a" (eax), "d" (edx), "c" (index)); + asm volatile("xsetbv" :: "a" (eax), "d" (edx), "c" (index) + : "memory"); } /*