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 D832BC63684 for ; Wed, 26 Jan 2022 10:04:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239572AbiAZKEB (ORCPT ); Wed, 26 Jan 2022 05:04:01 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51379 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233384AbiAZKD7 (ORCPT ); Wed, 26 Jan 2022 05:03:59 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643191439; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XrFLYJ9cry+WM5T0ZEL1s3Cr9YcXnG7PMN9SDbX6/ww=; b=OOK0kTTiqqPmQM2ACobTrTs3ejLh1gCFFy0tTBMNssqoDQEh7g/ig4mXcQcM7SH0OyXTl1 q7p4e86VzU4wVIvz9yWwKrsWEND/R7uBQ8jytmngBEfT5tT44/kfjobrMDQodJscFZUfOB 1vIRdp7Pbxwv+I2rXz7eHVVLUkR4CeI= Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-570-x5CTQOX0PHWkT9o4X0egsw-1; Wed, 26 Jan 2022 05:03:57 -0500 X-MC-Unique: x5CTQOX0PHWkT9o4X0egsw-1 Received: by mail-ed1-f69.google.com with SMTP id w15-20020a056402268f00b00408234dc1dfso5860495edd.16 for ; Wed, 26 Jan 2022 02:03:57 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=XrFLYJ9cry+WM5T0ZEL1s3Cr9YcXnG7PMN9SDbX6/ww=; b=dOMPMOoMYqK8bKClES0bodb9vFg+gJU1rkO0h/19MIRdK7TVTeLq2FLNgkx9r8a6gr dia0/WQRWFmLqCdmVMlSu7RiPfjkq33lOjeNJdawhd4LmEcn0OvESu0zyN+wRa3f7WVG eRRN+ECm7DLjzmTl5uu4z1lLcGZx3MuDcsXitnm9ols2ziCJ9rVz+vDDbGtMOiI93h8h xGzrY5H8g7bdyxj1Dx9npvV0sTuQ00ph6vGAe0yD6Xq5Ol1eiiRpeDPBI1+FKkiEAcux ClnvToQ/KnXBHXdBiW5nq6dbP6QPXys3fNmLyCKXSYqKeBh5ftaNRBzKXny/Y5lic8PF 1Jhg== X-Gm-Message-State: AOAM531OCZBHIgOlSfEeZ7AC9AnE+qa0gBk4B4dONPGMgmzAJt4pJ3SY no9Z+aFgkWVUOA7Hm9dLy2SRCwhJ7XMK+QnvdobZoDpxb9pHxzIyH9grdvvUnzl9PBQybYdzvI0 aEDV4w/zxNKT83fogLz2M5qph X-Received: by 2002:a17:906:cc84:: with SMTP id oq4mr20750935ejb.736.1643191436680; Wed, 26 Jan 2022 02:03:56 -0800 (PST) X-Google-Smtp-Source: ABdhPJyRQ+0XLF4POUmxWH8EJJr77JEz8GW0+2DZNmA1meDp2yb7dCZHSIEtz1s7LpmPIel02UXIsg== X-Received: by 2002:a17:906:cc84:: with SMTP id oq4mr20750919ejb.736.1643191436473; Wed, 26 Jan 2022 02:03:56 -0800 (PST) Received: from fedora (nat-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id rv9sm7151085ejb.216.2022.01.26.02.03.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Jan 2022 02:03:55 -0800 (PST) From: Vitaly Kuznetsov To: Joe Perches Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Igor Mammedov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini Subject: Re: [PATCH 2/2] KVM: x86: Use memcmp in kvm_cpuid_check_equal() In-Reply-To: <864dfbfdc44e288e99cf7baa3aa8f7c8568db507.camel@perches.com> References: <20220124103606.2630588-1-vkuznets@redhat.com> <20220124103606.2630588-3-vkuznets@redhat.com> <864dfbfdc44e288e99cf7baa3aa8f7c8568db507.camel@perches.com> Date: Wed, 26 Jan 2022 11:03:54 +0100 Message-ID: <878rv2izjp.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Joe Perches writes: > On Mon, 2022-01-24 at 11:36 +0100, Vitaly Kuznetsov wrote: >> kvm_cpuid_check_equal() should also check .flags equality but instead >> of adding it to the existing check, just switch to using memcmp() for >> the whole 'struct kvm_cpuid_entry2'. > > Is the struct padding guaranteed to be identical ? > Well, yes (or we're all doomeed): - 'struct kvm_cpuid_entry2' is part of KVM userspace ABI, it is supposed to be stable. - Here we compare structs which come from the same userspace during one session (vCPU fd stays open), I can't imagine how structure layout can change on-the-fly. -- Vitaly