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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 6C888C4BA2D for ; Wed, 26 Feb 2020 23:16:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 42C3E222C2 for ; Wed, 26 Feb 2020 23:16:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727922AbgBZXQT (ORCPT ); Wed, 26 Feb 2020 18:16:19 -0500 Received: from mga04.intel.com ([192.55.52.120]:3614 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727749AbgBZXQS (ORCPT ); Wed, 26 Feb 2020 18:16:18 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Feb 2020 15:16:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,489,1574150400"; d="scan'208";a="410797453" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.202]) by orsmga005.jf.intel.com with ESMTP; 26 Feb 2020 15:16:18 -0800 From: Sean Christopherson To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org Cc: "H. Peter Anvin" , linux-kernel@vger.kernel.org, Dave Hansen , Jacob Keller Subject: [PATCH] x86/pkeys: Manually set X86_FEATURE_OSPKE to preserve existing changes Date: Wed, 26 Feb 2020 15:16:15 -0800 Message-Id: <20200226231615.13664-1-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.24.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Explicitly set X86_FEATURE_OSPKE via set_cpu_cap() instead of calling get_cpu_cap() to pull the feature bit from CPUID after enabling CR4.PKE. Invoking get_cpu_cap() effectively wipes out any {set,clear}_cpu_cap() changes that were made between this_cpu->c_init() and setup_pku(), as all non-synthetic feature words are reinitialized from the CPU's CPUID values. Blasting away capability updates manifests most visibility when running on a VMX capable CPU, but with VMX disabled by BIOS. To indicate that VMX is disabled, init_ia32_feat_ctl() clears X86_FEATURE_VMX, using clear_cpu_cap() instead of setup_clear_cpu_cap() so that KVM can report which CPU is misconfigured (KVM needs to probe every CPU anyways). Restoring X86_FEATURE_VMX from CPUID causes KVM to think VMX is enabled, ultimately leading to an unexpected #GP when KVM attempts to do VMXON. Arguably, init_ia32_feat_ctl() should use setup_clear_cpu_cap() and let KVM figure out a different way to report the misconfigured CPU, but VMX is not the only feature bit that is affected, i.e. there is precedent that tweaking feature bits via {set,clear}_cpu_cap() after ->c_init() is expected to work. Most notably, x86_init_rdrand()'s clearing of X86_FEATURE_RDRAND when RDRAND malfunctions is also overwritten. Fixes: 0697694564c8 ("x86/mm/pkeys: Actually enable Memory Protection Keys in the CPU") Cc: stable@vger.kernel.org Cc: Dave Hansen Reported-by: Jacob Keller Signed-off-by: Sean Christopherson --- I considered adding a WARN_ON check of cpuid_ecx(7) to ensure OSPKE is set and bail if it's not, but that seemed like useless paranoia. I don't love that using clear_cpu_cap() is a bit fragile, especially where init_ia32_feat_ctl() is concerned, but the existing RDRAND usage, which predates setup_pku(), makes a pretty strong argument that setup_pku() is in the wrong. The other potential issue is late microcode updates, which refreshes the feature bits from CPUID, but at least in that case the kernel will print a warning if something changed. arch/x86/kernel/cpu/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 52c9bfbbdb2a..4cdb123ff66a 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -445,7 +445,7 @@ static __always_inline void setup_pku(struct cpuinfo_x86 *c) * cpuid bit to be set. We need to ensure that we * update that bit in this CPU's "cpu_info". */ - get_cpu_cap(c); + set_cpu_cap(c, X86_FEATURE_OSPKE); } #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS -- 2.24.1