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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6DF49EB64DD for ; Tue, 18 Jul 2023 23:17:22 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7C36528000D; Tue, 18 Jul 2023 19:17:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 773B58D0012; Tue, 18 Jul 2023 19:17:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6141B28000D; Tue, 18 Jul 2023 19:17:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 4EFB28D0012 for ; Tue, 18 Jul 2023 19:17:21 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id D754780518 for ; Tue, 18 Jul 2023 23:17:20 +0000 (UTC) X-FDA: 81026295840.14.688394B Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by imf14.hostedemail.com (Postfix) with ESMTP id DD1B2100015 for ; Tue, 18 Jul 2023 23:17:17 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=AX5tK4nk; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf14.hostedemail.com: domain of dave.hansen@intel.com designates 134.134.136.31 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689722238; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Gisme+V53rHtdQIFle9JRWCBOYBnkfMGNTfgsIsX/70=; b=7yJsMS8RROv36BAiRHBzwCzKc5CEeXX9o16Fqbd35+1TNqScueKF7aDuFeZOGo6lvJfXXK Nj/LRw6DD216IWJfi683d/nW2yeVlM26VBFTdiDta55f/9qvL1xcWmhJVS+6wiVQM/Q6DI Tv7m+VUKAGodeNshwDn68Tlx6yD+kJo= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=AX5tK4nk; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf14.hostedemail.com: domain of dave.hansen@intel.com designates 134.134.136.31 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689722238; a=rsa-sha256; cv=none; b=dU8dRZjeOrwf10DPEe7U19ODHn6o0rL8/Dm9Xhc01Io8wXKEpX7Chk3GilyRtvS7Fr/QOO l2sMqyfHB/RO3uaVX1wc8U99rYDqXhBbkE78nyVptV/2E/gj9agQG+SHtbXag6600Yl4Y3 7m2dqMhwuCUir3dDxswP5sa2dUkSCvE= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689722237; x=1721258237; h=message-id:date:mime-version:from:subject:to:cc: references:in-reply-to:content-transfer-encoding; bh=LKaFukftyjgRVkggmhjfkR3N5wbjbrueS9ivB5r4O8o=; b=AX5tK4nkRMzqQ7fGmfL68kKX+7q1sPjURntAJs/g70Kj5Kd3W+65iI0k opZMCK14Sp0zDZ+7wHZtboc7KzZneyxkLQvwIyzyXKgon1EvTWsgJrT2K umr4p0eySunY8PXkLiLTNA6yV2InyitasiKp1s9rS6i6/jyGRnQXhtw2S 0HaWCfu5B3MJEzuY2X86WPBDloSHC9R+6LhPIREgyvqRV2US8p6gSd+Fl cR2ZguvQSJASle5Cm0+N7p/F/fS2/o0GV7BnAvv9zYB2Ni6YP6Ph8NM+S WM5FE7zJPAH2aK/U5GvLcVXdzjDxwd+9cyQcwU5DV8V6ZVHiZI5Vt0/ys g==; X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="430095237" X-IronPort-AV: E=Sophos;i="6.01,215,1684825200"; d="scan'208";a="430095237" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 16:17:15 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10775"; a="837450299" X-IronPort-AV: E=Sophos;i="6.01,215,1684825200"; d="scan'208";a="837450299" Received: from unknown (HELO [10.209.37.195]) ([10.209.37.195]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Jul 2023 16:17:11 -0700 Message-ID: <396d0e29-defc-e207-2cbd-fe7137e798ad@intel.com> Date: Tue, 18 Jul 2023 16:17:11 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 From: Dave Hansen Subject: Re: [PATCH RFC v9 08/51] x86/speculation: Do not enable Automatic IBRS if SEV SNP is enabled To: Kim Phillips , Michael Roth , kvm@vger.kernel.org Cc: linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, liam.merwick@oracle.com, zhi.a.wang@intel.com References: <20230612042559.375660-1-michael.roth@amd.com> <20230612042559.375660-9-michael.roth@amd.com> <696ea7fe-3294-f21b-3bc0-3f8cc0a718e9@intel.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: DD1B2100015 X-Stat-Signature: jzj13nxqsxtzqsoychqzc75hjfqzy3tz X-Rspam-User: X-HE-Tag: 1689722237-211761 X-HE-Meta: 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 5snyBCTJ oHZutAO8BBya8YDTOrvfTs114uq09pEhBfoOT0u2AlDbigR0hrB9bJMUIb/9Z080/jog4j7ZLnAUt02hLagZMjtlDqSmuzesCRLxAWcDs6NCB07QWa/Xk/L70vmqcyWPl7UPxpYSYfhoB7SocyXbjRhR9Mw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/18/23 15:34, Kim Phillips wrote: ... > Automatic IBRS provides protection to [1]: > >  - Processes running at CPL=0 >  - Processes running as host when Secure Nested Paging (SEV-SNP) is enabled > > i.e., > >     (CPL < 3) || ((ASID == 0) && SNP) > > Because of this limitation, do not enable Automatic IBRS when SNP is > enabled. Gah, I found that hard to parse. I think it's because you're talking about an SEV-SNP host in one part and "SNP" in the other but _meaning_ SNP host and SNP guest. Could I maybe suggest that you folks follow the TDX convention and actually add _GUEST and _HOST to the feature name be explicit about which side is which? > Instead, fall back to retpolines. Now I'm totally lost. This is talking about falling back to retpolines ... in the kernel. But "Automatic IBRS provides protection to ... CPL < 3", aka. the kernel. > Note that the AutoIBRS feature may continue to be used within the > guest. What is this trying to say? "AutoIBRS can still be used in a guest since it protects CPL < 3" or "The AutoIBRS bits can still be twiddled within the guest even though it doesn't do any good" ? > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c > index 8cd4126d8253..311c0a6422b5 100644 > --- a/arch/x86/kernel/cpu/common.c > +++ b/arch/x86/kernel/cpu/common.c > @@ -1348,7 +1348,8 @@ static void __init cpu_set_bug_bits(struct > cpuinfo_x86 *c) >       * AMD's AutoIBRS is equivalent to Intel's eIBRS - use the Intel feature >       * flag and protect from vendor-specific bugs via the whitelist. >       */ > -    if ((ia32_cap & ARCH_CAP_IBRS_ALL) || cpu_has(c, X86_FEATURE_AUTOIBRS)) { > +    if ((ia32_cap & ARCH_CAP_IBRS_ALL) || (cpu_has(c, X86_FEATURE_AUTOIBRS) && > +        !cpu_feature_enabled(X86_FEATURE_SEV_SNP))) { >          setup_force_cpu_cap(X86_FEATURE_IBRS_ENHANCED); >          if (!cpu_matches(cpu_vuln_whitelist, NO_EIBRS_PBRSB) && >              !(ia32_cap & ARCH_CAP_PBRSB_NO))