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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46950C433EF for ; Sun, 23 Jan 2022 06:22:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231671AbiAWGWk (ORCPT ); Sun, 23 Jan 2022 01:22:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229549AbiAWGWj (ORCPT ); Sun, 23 Jan 2022 01:22:39 -0500 Received: from mail-pg1-x532.google.com (mail-pg1-x532.google.com [IPv6:2607:f8b0:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 597C0C06173B; Sat, 22 Jan 2022 22:22:39 -0800 (PST) Received: by mail-pg1-x532.google.com with SMTP id i8so12028139pgt.13; Sat, 22 Jan 2022 22:22:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:organization:in-reply-to :content-transfer-encoding; bh=7nNuF1SdnxMhoyP6add+HcXWspOBLXOW0pQRUR9FJJY=; b=fkIVJBi55hdrmbtKJ6BFfYKgQa14CppyiD0sQhYJt5j5Y59Is/EgCYY+Q2N3NMme5U wU5qfJfA34wlMreVYEKjy6EvfmroXJKtaW1nZbRnbxw2AcrbeVBa8pqZQBgixmFPKRIH pnLbq1MacbJiajySAxRQxrFvLAkALG+3HXky1pxa4XfWBsuLUqoy1T3wiij9uX0tcD8n dT+qODwkyS3GIWZ6e6uRTHb088FmGUXB6Uw+Wa649a0HXxa8LtQNsNgHP5G1rXcZcHX5 g1u3Tai+llRViE6LWiX7Va013mKGfH7JSTBtk7Ba0Ksnj4KK9ILzybKxKr5FCvb5AE0c 4T/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:organization:in-reply-to :content-transfer-encoding; bh=7nNuF1SdnxMhoyP6add+HcXWspOBLXOW0pQRUR9FJJY=; b=7xHfKplAIyGdWfhFlLbv1K7kS68zBXo0+yuWoACWMQvOPzhMp8NGAcYB9mwUQH3UG6 Zb8jP2IKTqKBRB47Fw507e//aS93Oq9fDMfucIxnBd5XhKyS7Wmyf/TZImDKdYtYFVhU RiO72KyQJjAwDqFFLMaM26iNvn/oK+d/3bHEzMiAICNDZ0tznEuXU5Fy4Wo5aPTVpZQE EkVpqH5DbEythfVZu+ZLz4dXDApykAuFojgS4Bedr9BPt4LONd//bXyRHFp5jqjPAaZG 4u+BSt2aJfJOvvEghIzXxAU44FGqrt5oRtvgvyLl8RvOAcr+U5bTm7HM6z3qIgAYjxk1 zIXA== X-Gm-Message-State: AOAM532S4eIqJ0ZU6XVI1r+ZrXqkGbQfqMhXYSX2Gd/ErRwKHydzCCfb TEKrlyMGalAMlsHamW0oAmWubdCtVPvCFg== X-Google-Smtp-Source: ABdhPJxhU44ebUVZ8QYgtUWW60Oxt72uQ6OxQPmZcJynVnLGDqMCmcbQZcX+RqlfFp297EmiwpFtHg== X-Received: by 2002:a63:2bd5:: with SMTP id r204mr8025431pgr.232.1642918958902; Sat, 22 Jan 2022 22:22:38 -0800 (PST) Received: from [192.168.255.10] ([103.7.29.32]) by smtp.gmail.com with ESMTPSA id v15sm8444918pgc.52.2022.01.22.22.22.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 22 Jan 2022 22:22:38 -0800 (PST) Message-ID: <75fe2317-4159-adbe-30f8-5bbd2f5e9d11@gmail.com> Date: Sun, 23 Jan 2022 14:22:28 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v6 04/21] kvm: x86: Exclude unpermitted xfeatures at KVM_GET_SUPPORTED_CPUID Content-Language: en-US To: Paolo Bonzini , Jing Liu Cc: guang.zeng@intel.com, kevin.tian@intel.com, seanjc@google.com, tglx@linutronix.de, wei.w.wang@intel.com, yang.zhong@intel.com, "linux-kernel@vger.kernel.org" , kvm list References: <20220107185512.25321-1-pbonzini@redhat.com> <20220107185512.25321-5-pbonzini@redhat.com> From: Like Xu Organization: Tencent In-Reply-To: <20220107185512.25321-5-pbonzini@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/1/2022 2:54 am, Paolo Bonzini wrote: > From: Jing Liu > > KVM_GET_SUPPORTED_CPUID should not include any dynamic xstates in > CPUID[0xD] if they have not been requested with prctl. Otherwise > a process which directly passes KVM_GET_SUPPORTED_CPUID to > KVM_SET_CPUID2 would now fail even if it doesn't intend to use a > dynamically enabled feature. Userspace must know that prctl is > required and allocate >4K xstate buffer before setting any dynamic > bit. > > Suggested-by: Paolo Bonzini > Signed-off-by: Jing Liu > Signed-off-by: Yang Zhong > Message-Id: <20220105123532.12586-5-yang.zhong@intel.com> > Signed-off-by: Paolo Bonzini > --- > Documentation/virt/kvm/api.rst | 4 ++++ > arch/x86/kvm/cpuid.c | 9 ++++++--- > 2 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 6b683dfea8f2..f4ea5e41a4d0 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -1687,6 +1687,10 @@ userspace capabilities, and with user requirements (for example, the > user may wish to constrain cpuid to emulate older hardware, or for > feature consistency across a cluster). > > +Dynamically-enabled feature bits need to be requested with > +``arch_prctl()`` before calling this ioctl. Feature bits that have not > +been requested are excluded from the result. > + > Note that certain capabilities, such as KVM_CAP_X86_DISABLE_EXITS, may > expose cpuid features (e.g. MONITOR) which are not supported by kvm in > its default configuration. If userspace enables such capabilities, it > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index f3e6fda6b858..eb52dde5deec 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -815,11 +815,13 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > goto out; > } > break; > - case 0xd: > - entry->eax &= supported_xcr0; > + case 0xd: { > + u64 guest_perm = xstate_get_guest_group_perm(); > + > + entry->eax &= supported_xcr0 & guest_perm; > entry->ebx = xstate_required_size(supported_xcr0, false); If we choose to exclude unpermitted xfeatures in the entry->eax, why do we choose to expose the size of unpermitted xfeatures in ebx and ecx? This seems to be an inconsistency, how about: diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 1bd4d560cbdd..193cbf56a5fa 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -888,12 +888,12 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) } break; case 0xd: { - u64 guest_perm = xstate_get_guest_group_perm(); + u64 supported_xcr0 = supported_xcr0 & xstate_get_guest_group_perm(); - entry->eax &= supported_xcr0 & guest_perm; + entry->eax &= supported_xcr0; entry->ebx = xstate_required_size(supported_xcr0, false); entry->ecx = entry->ebx; - entry->edx &= (supported_xcr0 & guest_perm) >> 32; + entry->edx &= supported_xcr0 >> 32; if (!supported_xcr0) break; It also helps to fix the CPUID_D_1_EBX and later for (i = 2; i < 64; ++i); Is there anything I've missed ? > entry->ecx = entry->ebx; > - entry->edx &= supported_xcr0 >> 32; > + entry->edx &= (supported_xcr0 & guest_perm) >> 32; > if (!supported_xcr0) > break; > > @@ -866,6 +868,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function) > entry->edx = 0; > } > break; > + } > case 0x12: > /* Intel SGX */ > if (!kvm_cpu_cap_has(X86_FEATURE_SGX)) {