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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 43693ECDE44 for ; Fri, 26 Oct 2018 18:15:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F28C120834 for ; Fri, 26 Oct 2018 18:15:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F28C120834 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727998AbeJ0Cxt (ORCPT ); Fri, 26 Oct 2018 22:53:49 -0400 Received: from mga09.intel.com ([134.134.136.24]:2974 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727595AbeJ0Cxt (ORCPT ); Fri, 26 Oct 2018 22:53:49 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Oct 2018 11:15:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,428,1534834800"; d="scan'208";a="85865858" Received: from schen9-desk.jf.intel.com (HELO [10.54.74.144]) ([10.54.74.144]) by orsmga006.jf.intel.com with ESMTP; 26 Oct 2018 11:15:35 -0700 Subject: Re: [Patch v3 03/13] x86/speculation: Add static key for Enhanced IBRS To: Waiman Long , Jiri Kosina , Thomas Gleixner Cc: Tom Lendacky , Ingo Molnar , Peter Zijlstra , Josh Poimboeuf , Andrea Arcangeli , David Woodhouse , Andi Kleen , Dave Hansen , Casey Schaufler , Asit Mallick , Arjan van de Ven , Jon Masters , linux-kernel@vger.kernel.org, x86@kernel.org References: From: Tim Chen Openpgp: preference=signencrypt Autocrypt: addr=tim.c.chen@linux.intel.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/26/2018 09:58 AM, Waiman Long wrote: > On 10/17/2018 01:59 PM, Tim Chen wrote: >> Add static key to indicate whether we are using Enhanced IBRS to mitigate >> Spectre v2. This will be used in later patches to disengage STIBP code >> for Spectre v2 mitigation as STIBP is not needed when Enhanced IBRS is >> in use. >> >> Signed-off-by: Tim Chen >> --- >> arch/x86/include/asm/nospec-branch.h | 3 +++ >> arch/x86/kernel/cpu/bugs.c | 4 ++++ >> 2 files changed, 7 insertions(+) >> >> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h >> index fd2a8c1..d57e84e 100644 >> --- a/arch/x86/include/asm/nospec-branch.h >> +++ b/arch/x86/include/asm/nospec-branch.h >> @@ -3,6 +3,7 @@ >> #ifndef _ASM_X86_NOSPEC_BRANCH_H_ >> #define _ASM_X86_NOSPEC_BRANCH_H_ >> >> +#include >> #include >> #include >> #include >> @@ -228,6 +229,8 @@ enum ssb_mitigation { >> extern char __indirect_thunk_start[]; >> extern char __indirect_thunk_end[]; >> >> +DECLARE_STATIC_KEY_FALSE(spectre_v2_enhanced_ibrs); >> + >> /* >> * On VMEXIT we must ensure that no RSB predictions learned in the guest >> * can be followed in the host, by overwriting the RSB completely. Both >> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c >> index b2f6b8b..2fc7b4e 100644 >> --- a/arch/x86/kernel/cpu/bugs.c >> +++ b/arch/x86/kernel/cpu/bugs.c >> @@ -142,6 +142,9 @@ static const char *spectre_v2_strings[] = { >> [SPECTRE_V2_IBRS_ENHANCED] = "Mitigation: Enhanced IBRS", >> }; >> >> +DEFINE_STATIC_KEY_FALSE(spectre_v2_enhanced_ibrs); >> +EXPORT_SYMBOL(spectre_v2_enhanced_ibrs); >> + >> #undef pr_fmt >> #define pr_fmt(fmt) "Spectre V2 : " fmt >> >> @@ -386,6 +389,7 @@ static void __init spectre_v2_select_mitigation(void) >> /* Force it so VMEXIT will restore correctly */ >> x86_spec_ctrl_base |= SPEC_CTRL_IBRS; >> wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base); >> + static_branch_enable(&spectre_v2_enhanced_ibrs); >> goto specv2_set_mode; >> } >> if (IS_ENABLED(CONFIG_RETPOLINE)) > > Why you need a static key for enhanced IBRS? It is supposed to be set at > boot time and never get changed after that. It will be easier to use a > feature bit for that instead. We usually use static key when the value > can be changed at run time. > We're close to running out of the feature bits. So I'm trying not to use those. Tim