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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 59363C43461 for ; Wed, 16 Sep 2020 20:56:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0156621941 for ; Wed, 16 Sep 2020 20:56:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726660AbgIPU4S (ORCPT ); Wed, 16 Sep 2020 16:56:18 -0400 Received: from mga12.intel.com ([192.55.52.136]:51996 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726255AbgIPQww (ORCPT ); Wed, 16 Sep 2020 12:52:52 -0400 IronPort-SDR: gWixcFHN3jAoJ6gFiDZSr7Ro9EuMOUod1GmMM5zhwcoPNfmbrpWhFohWWYwAfD/cOy/eOKS7sE FRNdkuXsirmQ== X-IronPort-AV: E=McAfee;i="6000,8403,9746"; a="139024811" X-IronPort-AV: E=Sophos;i="5.76,433,1592895600"; d="scan'208";a="139024811" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2020 09:49:25 -0700 IronPort-SDR: 9XPDFBcq2CYfeTnmvu0XQg2wz09WgX6OsPOZPKgeySGJ/G5i9vFKH+uih3kTRLcOlE6xtadwXz BKL5zDVguypQ== X-IronPort-AV: E=Sophos;i="5.76,433,1592895600"; d="scan'208";a="307109500" Received: from sjchrist-ice.jf.intel.com (HELO sjchrist-ice) ([10.54.31.34]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2020 09:49:24 -0700 Date: Wed, 16 Sep 2020 09:49:23 -0700 From: Sean Christopherson To: Tom Lendacky Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Paolo Bonzini , Jim Mattson , Joerg Roedel , Vitaly Kuznetsov , Wanpeng Li , Borislav Petkov , Ingo Molnar , Thomas Gleixner , Brijesh Singh Subject: Re: [RFC PATCH 08/35] KVM: SVM: Prevent debugging under SEV-ES Message-ID: <20200916164923.GC10227@sjchrist-ice> References: <58093c542b5b442b88941828595fb2548706f1bf.1600114548.git.thomas.lendacky@amd.com> <20200914212601.GA7192@sjchrist-ice> <20200915163010.GB8420@sjchrist-ice> <5e816811-450f-b732-76f7-6130479642e0@amd.com> <20200916160210.GA10227@sjchrist-ice> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 16, 2020 at 11:38:38AM -0500, Tom Lendacky wrote: > > > On 9/16/20 11:02 AM, Sean Christopherson wrote: > > On Wed, Sep 16, 2020 at 10:11:10AM -0500, Tom Lendacky wrote: > >> On 9/15/20 3:13 PM, Tom Lendacky wrote: > >>> On 9/15/20 11:30 AM, Sean Christopherson wrote: > >>>> I don't quite follow the "doesn't mean debugging can't be done in the future". > >>>> Does that imply that debugging could be supported for SEV-ES guests, even if > >>>> they have an encrypted VMSA? > >>> > >>> Almost anything can be done with software. It would require a lot of > >>> hypervisor and guest code and changes to the GHCB spec, etc. So given > >>> that, probably just the check for arch.guest_state_protected is enough for > >>> now. I'll just need to be sure none of the debugging paths can be taken > >>> before the VMSA is encrypted. > >> > >> So I don't think there's any guarantee that the KVM_SET_GUEST_DEBUG ioctl > >> couldn't be called before the VMSA is encrypted, meaning I can't check the > >> arch.guest_state_protected bit for that call. So if we really want to get > >> rid of the allow_debug() op, I'd need some other way to indicate that this > >> is an SEV-ES / protected state guest. > > > > Would anything break if KVM "speculatively" set guest_state_protected before > > LAUNCH_UPDATE_VMSA? E.g. does KVM need to emulate before LAUNCH_UPDATE_VMSA? > > Yes, the way the code is set up, the guest state (VMSA) is initialized in > the same way it is today (mostly) and that state is encrypted by the > LAUNCH_UPDATE_VMSA call. I check the guest_state_protected bit to decide > on whether to direct the updates to the real VMSA (before it's encrypted) > or the GHCB (that's the get_vmsa() function from patch #5). Ah, gotcha. Would it work to set guest_state_protected[*] from time zero, and move vmsa_encrypted to struct vcpu_svm? I.e. keep vmsa_encrypted, but use it only for guiding get_vmsa() and related behavior.