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=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 D2DE2C3F2D1 for ; Tue, 3 Mar 2020 02:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ADC2624673 for ; Tue, 3 Mar 2020 02:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727228AbgCCC1x (ORCPT ); Mon, 2 Mar 2020 21:27:53 -0500 Received: from mga11.intel.com ([192.55.52.93]:12164 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726970AbgCCC1x (ORCPT ); Mon, 2 Mar 2020 21:27:53 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Mar 2020 18:27:52 -0800 X-IronPort-AV: E=Sophos;i="5.70,509,1574150400"; d="scan'208";a="233433400" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.255.30.67]) ([10.255.30.67]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-SHA; 02 Mar 2020 18:27:50 -0800 Subject: Re: [PATCH 1/6] KVM: x86: Fix tracing of CPUID.function when function is out-of-range To: Sean Christopherson , Jan Kiszka Cc: Paolo Bonzini , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200302195736.24777-1-sean.j.christopherson@intel.com> <20200302195736.24777-2-sean.j.christopherson@intel.com> <188dc96a-6a3b-4021-061a-0f11cbb9f177@siemens.com> <20200302204940.GG6244@linux.intel.com> From: Xiaoyao Li Message-ID: <16e902a8-7883-0b67-d4ee-73e8fe22f955@intel.com> Date: Tue, 3 Mar 2020 10:27:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200302204940.GG6244@linux.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed 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 3/3/2020 4:49 AM, Sean Christopherson wrote: > On Mon, Mar 02, 2020 at 09:26:54PM +0100, Jan Kiszka wrote: >> On 02.03.20 20:57, Sean Christopherson wrote: >>> Rework kvm_cpuid() to query entry->function when adjusting the output >>> values so that the original function (in the aptly named "function") is >>> preserved for tracing. This fixes a bug where trace_kvm_cpuid() will >>> trace the max function for a range instead of the requested function if >>> the requested function is out-of-range and an entry for the max function >>> exists. >>> >>> Fixes: 43561123ab37 ("kvm: x86: Improve emulation of CPUID leaves 0BH and 1FH") >>> Reported-by: Jan Kiszka >>> Cc: Jim Mattson >>> Cc: Xiaoyao Li >>> Signed-off-by: Sean Christopherson >>> --- >>> arch/x86/kvm/cpuid.c | 15 +++++++-------- >>> 1 file changed, 7 insertions(+), 8 deletions(-) >>> >>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c >>> index b1c469446b07..6be012937eba 100644 >>> --- a/arch/x86/kvm/cpuid.c >>> +++ b/arch/x86/kvm/cpuid.c >>> @@ -997,12 +997,12 @@ static bool cpuid_function_in_range(struct kvm_vcpu *vcpu, u32 function) >>> return max && function <= max->eax; >>> } >>> +/* Returns true if the requested leaf/function exists in guest CPUID. */ >>> bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, >>> u32 *ecx, u32 *edx, bool check_limit) >>> { >>> - u32 function = *eax, index = *ecx; >>> + const u32 function = *eax, index = *ecx; >>> struct kvm_cpuid_entry2 *entry; >>> - struct kvm_cpuid_entry2 *max; >>> bool found; >>> entry = kvm_find_cpuid_entry(vcpu, function, index); >>> @@ -1015,18 +1015,17 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, >>> */ >>> if (!entry && check_limit && !guest_cpuid_is_amd(vcpu) && >>> !cpuid_function_in_range(vcpu, function)) { >>> - max = kvm_find_cpuid_entry(vcpu, 0, 0); >>> - if (max) { >>> - function = max->eax; >>> - entry = kvm_find_cpuid_entry(vcpu, function, index); >>> - } >>> + entry = kvm_find_cpuid_entry(vcpu, 0, 0); >>> + if (entry) >>> + entry = kvm_find_cpuid_entry(vcpu, entry->eax, index); >>> } >>> if (entry) { >>> *eax = entry->eax; >>> *ebx = entry->ebx; >>> *ecx = entry->ecx; >>> *edx = entry->edx; >>> - if (function == 7 && index == 0) { >>> + >>> + if (entry->function == 7 && index == 0) { >>> u64 data; >>> if (!__kvm_get_msr(vcpu, MSR_IA32_TSX_CTRL, &data, true) && >>> (data & TSX_CTRL_CPUID_CLEAR)) >>> >> >> What about the !entry case below this? It was impacted by the function >> capping so far, not it's no longer. > > Hmm, the only way the output would be different is in a really contrived > scenario where userspace doesn't provide an entry for the max basic leaf. > > The !entry path can only be reached with "orig_function != function" if > orig_function is out of range and there is no entry for the max basic leaf. > The adjustments for 0xb/0x1f require the max basic leaf to be 0xb or 0x1f, > and to take effect with !entry would require there to be a CPUID.max.1 but > not a CPUID.max.0. That'd be a violation of Intel's SDM, i.e. it's bogus > userspace input and IMO can be ignored. > Sorry I cannot catch you. Why it's a violation of Intel's SDM? Supposing the max basic is 0x1f, and it queries cpuid(0x20, 0x5), it should return cpuid(0x1f, 0x5). But based on this patch, it returns all zeros.