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 8A96FC433F5 for ; Tue, 19 Apr 2022 13:33:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244226AbiDSNgM (ORCPT ); Tue, 19 Apr 2022 09:36:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58314 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243962AbiDSNgJ (ORCPT ); Tue, 19 Apr 2022 09:36:09 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 5A2882252A for ; Tue, 19 Apr 2022 06:33:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650375205; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3Q1ZKb2vhm6xzFB6dH4S0BphbsICw4w11AsX7JXEyf0=; b=F/qpDkwWYl95Jj79cY3FrZ6G/vy75MaDSsnEcKM0J18vqIx6GbCAxAdOap9gP332gLIbXC RiTbWOeosVBwBcBXJqSMNdXYpmmmb8CElG46k/hqxdKjINqkE3V2U33F6t9qkkviJX2wos urC+bBMcmzG1HwPqjbyo8PVj58yL3tU= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-599-ZMIdkErAO2yUJ32DJEJPxQ-1; Tue, 19 Apr 2022 09:33:22 -0400 X-MC-Unique: ZMIdkErAO2yUJ32DJEJPxQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D8A683804500; Tue, 19 Apr 2022 13:33:21 +0000 (UTC) Received: from [10.22.8.117] (unknown [10.22.8.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id 75D777C28; Tue, 19 Apr 2022 13:33:21 +0000 (UTC) Message-ID: Date: Tue, 19 Apr 2022 09:33:21 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: adding 'official' way to dump SEV VMSA Content-Language: en-US To: "Dr. David Alan Gilbert" , Dov Murik Cc: "kvm@vger.kernel.org" , qemu-devel , "Singh, Brijesh" , Tom Lendacky , "Daniel P. Berrange" , Paolo Bonzini References: <462cbf77-432a-c09c-6ec9-91556dc0f887@linux.ibm.com> From: Cole Robinson In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 4/14/22 4:25 AM, Dr. David Alan Gilbert wrote: > * Dov Murik (dovmurik@linux.ibm.com) wrote: >> Hi Cole, >> >> On 13/04/2022 16:36, Cole Robinson wrote: >>> Hi all, >>> >>> SEV-ES and SEV-SNP attestation require a copy of the initial VMSA to >>> validate the launch measurement. For developers dipping their toe into >>> SEV-* work, the easiest way to get sample VMSA data for their machine is >>> to grab it from a running VM. >>> >>> There's two techniques I've seen for that: patch some printing into >>> kernel __sev_launch_update_vmsa, or use systemtap like danpb's script >>> here: https://gitlab.com/berrange/libvirt/-/blob/lgtm/scripts/sev-vmsa.stp >>> >>> Seems like this could be friendlier though. I'd like to work on this if >>> others agree. >>> >>> Some ideas I've seen mentioned in passing: >>> >>> - debugfs entry in /sys/kernel/debug/kvm/.../vcpuX/ >>> - new KVM ioctl >>> - something with tracepoints >>> - some kind of dump in dmesg that doesn't require a patch >>> >>> Thoughts? >> >> >> Brijesh suggested to me to construct the VMSA without getting any info from >> the host (except number of vcpus), because the initial state of the vcpus >> is standard and known if you use QEMU and OVMF (but that's open for discussion). >> >> I took his approach (thanks Brijesh!) and now it's how we calculate expected >> SNP measurements in sev-snp-measure [1]. The relevant part for VMSA construction >> is in [2]. >> >> I plan to add SEV-ES and SEV measurements calculation to this >> library/program as well. > > Everyone seems to be writing one; you, Dan etc! > Yeah, I should have mentioned Dan's demo tool here: https://gitlab.com/berrange/libvirt/-/blob/lgtm/tools/virt-dom-sev-vmsa-tool.py Tyler Fanelli is looking at adding that functionality to sevctl too FWIW > I think I agree the right way is to build it programmatically rather > than taking a copy from the kernel; it's fairly simple, although the > scripts get increasingly hairy as you deal with more and more VMM's and > firmwares. > Agreed. A nice way to dump VMSA from the kernel will be useful for debugging, or extending these scripts to support different VMMs. > I think I'd like to see a new ioctl to read the initial VMSA, primarily > as a way of debugging so you can see what VMSA you have when something > goes wrong. > debugfs seems simpler for the dev user (accessing a file per CPU vs code to call ioctl), but beyond that I don't have any insight. Is there a reason you think ioctl and not debugfs? Thanks, Cole 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 936E0C433F5 for ; Tue, 19 Apr 2022 13:34:19 +0000 (UTC) Received: from localhost ([::1]:36202 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ngnzm-00050t-F6 for qemu-devel@archiver.kernel.org; Tue, 19 Apr 2022 09:34:18 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43242) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ngnz1-0004IG-7L for qemu-devel@nongnu.org; Tue, 19 Apr 2022 09:33:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:57745) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ngnyx-0002uG-VV for qemu-devel@nongnu.org; Tue, 19 Apr 2022 09:33:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650375205; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3Q1ZKb2vhm6xzFB6dH4S0BphbsICw4w11AsX7JXEyf0=; b=F/qpDkwWYl95Jj79cY3FrZ6G/vy75MaDSsnEcKM0J18vqIx6GbCAxAdOap9gP332gLIbXC RiTbWOeosVBwBcBXJqSMNdXYpmmmb8CElG46k/hqxdKjINqkE3V2U33F6t9qkkviJX2wos urC+bBMcmzG1HwPqjbyo8PVj58yL3tU= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-599-ZMIdkErAO2yUJ32DJEJPxQ-1; Tue, 19 Apr 2022 09:33:22 -0400 X-MC-Unique: ZMIdkErAO2yUJ32DJEJPxQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D8A683804500; Tue, 19 Apr 2022 13:33:21 +0000 (UTC) Received: from [10.22.8.117] (unknown [10.22.8.117]) by smtp.corp.redhat.com (Postfix) with ESMTP id 75D777C28; Tue, 19 Apr 2022 13:33:21 +0000 (UTC) Message-ID: Date: Tue, 19 Apr 2022 09:33:21 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: adding 'official' way to dump SEV VMSA Content-Language: en-US To: "Dr. David Alan Gilbert" , Dov Murik References: <462cbf77-432a-c09c-6ec9-91556dc0f887@linux.ibm.com> From: Cole Robinson In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Received-SPF: pass client-ip=170.10.129.124; envelope-from=crobinso@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tom Lendacky , "Daniel P. Berrange" , "kvm@vger.kernel.org" , qemu-devel , Paolo Bonzini , "Singh, Brijesh" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 4/14/22 4:25 AM, Dr. David Alan Gilbert wrote: > * Dov Murik (dovmurik@linux.ibm.com) wrote: >> Hi Cole, >> >> On 13/04/2022 16:36, Cole Robinson wrote: >>> Hi all, >>> >>> SEV-ES and SEV-SNP attestation require a copy of the initial VMSA to >>> validate the launch measurement. For developers dipping their toe into >>> SEV-* work, the easiest way to get sample VMSA data for their machine is >>> to grab it from a running VM. >>> >>> There's two techniques I've seen for that: patch some printing into >>> kernel __sev_launch_update_vmsa, or use systemtap like danpb's script >>> here: https://gitlab.com/berrange/libvirt/-/blob/lgtm/scripts/sev-vmsa.stp >>> >>> Seems like this could be friendlier though. I'd like to work on this if >>> others agree. >>> >>> Some ideas I've seen mentioned in passing: >>> >>> - debugfs entry in /sys/kernel/debug/kvm/.../vcpuX/ >>> - new KVM ioctl >>> - something with tracepoints >>> - some kind of dump in dmesg that doesn't require a patch >>> >>> Thoughts? >> >> >> Brijesh suggested to me to construct the VMSA without getting any info from >> the host (except number of vcpus), because the initial state of the vcpus >> is standard and known if you use QEMU and OVMF (but that's open for discussion). >> >> I took his approach (thanks Brijesh!) and now it's how we calculate expected >> SNP measurements in sev-snp-measure [1]. The relevant part for VMSA construction >> is in [2]. >> >> I plan to add SEV-ES and SEV measurements calculation to this >> library/program as well. > > Everyone seems to be writing one; you, Dan etc! > Yeah, I should have mentioned Dan's demo tool here: https://gitlab.com/berrange/libvirt/-/blob/lgtm/tools/virt-dom-sev-vmsa-tool.py Tyler Fanelli is looking at adding that functionality to sevctl too FWIW > I think I agree the right way is to build it programmatically rather > than taking a copy from the kernel; it's fairly simple, although the > scripts get increasingly hairy as you deal with more and more VMM's and > firmwares. > Agreed. A nice way to dump VMSA from the kernel will be useful for debugging, or extending these scripts to support different VMMs. > I think I'd like to see a new ioctl to read the initial VMSA, primarily > as a way of debugging so you can see what VMSA you have when something > goes wrong. > debugfs seems simpler for the dev user (accessing a file per CPU vs code to call ioctl), but beyond that I don't have any insight. Is there a reason you think ioctl and not debugfs? Thanks, Cole