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 X-Spam-Level: X-Spam-Status: No, score=-19.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B35CDC433DB for ; Wed, 10 Feb 2021 02:38:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 78FE264E32 for ; Wed, 10 Feb 2021 02:38:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235450AbhBJChv (ORCPT ); Tue, 9 Feb 2021 21:37:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:33518 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235236AbhBJCec (ORCPT ); Tue, 9 Feb 2021 21:34:32 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1CBB964E4F; Wed, 10 Feb 2021 02:33:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1612924430; bh=pxRvt0tsVaEuuk2qoLNHxBo/G7OEcqiXIfY7y7MzhWc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RxXy1/kKWVHC3c9/4U5f+o4auHqMfsjhjj4/7fNQSUmxqE5CFGwEx0IahtuK0GwID Jp5NVbGGv8SqkojdNv+41XMDODuLEzAoSHx4Ia1RlODTWLOrU07KTccc2oNw4fw+qD 43KnI9dMCJUFU6LXakdlgHJusTiEiygWlQYkdq4i55jsP1dkI732W3Ssx84SxTPjLF 6BUy3VYtSNHaEPhvYL3YxcHkC0JqkFU00IIOZSzEwsBmNsK0kAPb2mEVEGYjjqF3Qv SKqBJGYTKXnB2VbJMz5il19EM4m49qSH3lm2G3Jr4DppHPDn9MwkirZs7viUWnmYbj z150x8QMlitew== From: Andy Lutomirski To: x86@kernel.org Cc: LKML , Dave Hansen , Alexei Starovoitov , Daniel Borkmann , Yonghong Song , Masami Hiramatsu , Andy Lutomirski Subject: [PATCH v2 02/14] x86/fault: Skip the AMD erratum #91 workaround on unaffected CPUs Date: Tue, 9 Feb 2021 18:33:34 -0800 Message-Id: <477173b7784bc28afb3e53d76ae5ef143917e8dd.1612924255.git.luto@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org According to the Revision Guide for AMD Athlon™ 64 and AMD Opteron™ Processors, only early revisions of family 0xF are affected. This will avoid unnecessarily fetching instruction bytes before sending SIGSEGV to user programs. Signed-off-by: Andy Lutomirski --- arch/x86/mm/fault.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 441c3e9b8971..818902b08c52 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -106,6 +106,15 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr, } } +static bool is_amd_k8_pre_npt(void) +{ + struct cpuinfo_x86 *c = &boot_cpu_data; + + return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) && + c->x86_vendor == X86_VENDOR_AMD && + c->x86 == 0xf && c->x86_model < 0x40); +} + static int is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) { @@ -113,6 +122,10 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr) unsigned char *instr; int prefetch = 0; + /* Erratum #91 affects AMD K8, pre-NPT CPUs */ + if (!is_amd_k8_pre_npt()) + return 0; + /* * If it was a exec (instruction fetch) fault on NX page, then * do not ignore the fault: -- 2.29.2