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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 BD8FBC433DB for ; Thu, 14 Jan 2021 09:59:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7338B23A3A for ; Thu, 14 Jan 2021 09:59:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727348AbhANJ7O (ORCPT ); Thu, 14 Jan 2021 04:59:14 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:47488 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726858AbhANJ7N (ORCPT ); Thu, 14 Jan 2021 04:59:13 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1610618268; 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=bVl5rOU+HrnFitoJh1CZVmjqhbF76mPBERzkT+db+eg=; b=N7N68pkrhClqNG77X4V1P6JkLHRwNGBD0tdXr1N9ljqM3IXg+Y+ZEshT5X7T9tu+sM5Apl Xu2rN7ClPqVW7FNdIs7xwLCLpvrk+WyHam6/DKVrNwXLUFntv14HuYtJLWXuZWkykseB+Q L3+00ESKmb3WzssqioRBNBgbOfYb+ec= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-540-kHdkw4xoNPOb6o2ftpJytw-1; Thu, 14 Jan 2021 04:57:46 -0500 X-MC-Unique: kHdkw4xoNPOb6o2ftpJytw-1 Received: by mail-ed1-f72.google.com with SMTP id x13so2188873edi.7 for ; Thu, 14 Jan 2021 01:57:46 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=bVl5rOU+HrnFitoJh1CZVmjqhbF76mPBERzkT+db+eg=; b=MivZq6oWD87g7nzfouMD6+8DG4fXP3uoRvF6g5rHhpF0CKHi8ckvtM5Z1Qf8CYsiP7 YMgqDg3U8s1ykAfdA6ptNTJDztF/jqf+LuCurSYPRcm0MR6EUP9NnuNaTSuE6Ij545Qi gogMFOsfR7aB9x4fphEqr3nVSQ1KKS4YXQbBf3lCLIVRsn5hpSlC48Z1c0y12RX5MVZ1 JZEFbXmbs66jaGWkGvC9a9oEaxBybfbdowCUX0IS0HnoKT4rgzTIr+1as5lH5hNH5JSH BDaeziKm2/OLyR5COopdq8Iww2Jh2I6En1x1W4b+VBDbhWZhyfwORYZ8L6B8Y0EUXSyg ycSA== X-Gm-Message-State: AOAM530U99ZbxvJtRFyDKlT3++X/Qfy6MXmjQQYgFuo0sGO+BzfgOWVy kmrBEiIBEQK/knYEVZMyNIDHHo5JBrbYqWf4M0DT++lS+BISqH/Ng3eNKCzxJVWo7kv6iG1Kkh3 n9y10RGRv2863 X-Received: by 2002:a17:906:13da:: with SMTP id g26mr4603909ejc.285.1610618265431; Thu, 14 Jan 2021 01:57:45 -0800 (PST) X-Google-Smtp-Source: ABdhPJxNXN6RszazPqP4XbGtwo9cKyptdXFcfTwvzeumtC/0//AypLHdwmbOzlCcz0HUzLpqpgIjUA== X-Received: by 2002:a17:906:13da:: with SMTP id g26mr4603901ejc.285.1610618265292; Thu, 14 Jan 2021 01:57:45 -0800 (PST) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id m5sm1770704eja.11.2021.01.14.01.57.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Jan 2021 01:57:44 -0800 (PST) From: Vitaly Kuznetsov To: Sean Christopherson Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson Subject: Re: [PATCH 6/7] KVM: x86: hyper-v: Make Hyper-V emulation enablement conditional In-Reply-To: References: <20210113143721.328594-1-vkuznets@redhat.com> <20210113143721.328594-7-vkuznets@redhat.com> Date: Thu, 14 Jan 2021 10:57:43 +0100 Message-ID: <87v9bz7sdk.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Sean Christopherson writes: > On Wed, Jan 13, 2021, Vitaly Kuznetsov wrote: >> Hyper-V emulation is enabled in KVM unconditionally. This is bad at least >> from security standpoint as it is an extra attack surface. Ideally, there >> should be a per-VM capability explicitly enabled by VMM but currently it > > Would adding a module param buy us anything (other than complexity)? > A tiny bit, yes. This series is aimed at protecting KVM from 'curious guests' which can try to enable Hyper-V emulation features even when they don't show up in CPUID. A module parameter would help to protect against a malicious VMM which can still enable all these features. What I'm not sure about is how common Linux-guests-only deployments (where the parameter can actually get used) are as we'll have to keep it 'enabled' by default to avoid breaking existing deployments. -- Vitaly