From patchwork Sat Feb 1 18:51:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 11361339 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 345EB159A for ; Sat, 1 Feb 2020 18:56:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C48A20679 for ; Sat, 1 Feb 2020 18:56:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727066AbgBASw2 (ORCPT ); Sat, 1 Feb 2020 13:52:28 -0500 Received: from mga01.intel.com ([192.55.52.88]:57278 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726952AbgBASw1 (ORCPT ); Sat, 1 Feb 2020 13:52:27 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Feb 2020 10:52:26 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,390,1574150400"; d="scan'208";a="248075452" Received: from sjchrist-coffee.jf.intel.com ([10.54.74.202]) by orsmga002.jf.intel.com with ESMTP; 01 Feb 2020 10:52:25 -0800 From: Sean Christopherson To: Paolo Bonzini Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 08/61] KVM: x86: Warn on zero-size save state for valid CPUID 0xD.N sub-leaf Date: Sat, 1 Feb 2020 10:51:25 -0800 Message-Id: <20200201185218.24473-9-sean.j.christopherson@intel.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200201185218.24473-1-sean.j.christopherson@intel.com> References: <20200201185218.24473-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org WARN if the save state size for a valid XCR0-managed sub-leaf is zero, which would indicate a KVM or CPU bug. Add a comment to explain why KVM WARNs so the reader doesn't have to tease out the relevant bits from Intel's SDM and KVM's XCR0/XSS code. Signed-off-by: Sean Christopherson Reviewed-by: Vitaly Kuznetsov --- arch/x86/kvm/cpuid.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index fd9b29aa7abc..424dde41cb5d 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -677,10 +677,17 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, goto out; do_host_cpuid(&entry[i], function, idx); - if (entry[i].eax == 0) - continue; - if (WARN_ON_ONCE(entry[i].ecx & 1)) + + /* + * The @supported check above should have filtered out + * invalid sub-leafs as well as sub-leafs managed by + * IA32_XSS MSR. Only XCR0-managed sub-leafs should + * reach this point, and they should have a non-zero + * save state size. + */ + if (WARN_ON_ONCE(!entry[i].eax || (entry[i].ecx & 1))) continue; + entry[i].ecx = 0; entry[i].edx = 0; ++*nent;