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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07ECFC433EF for ; Thu, 4 Nov 2021 18:24:30 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 6E76761212 for ; Thu, 4 Nov 2021 18:24:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 6E76761212 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:33268 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mihPY-0007ZJ-Be for qemu-devel@archiver.kernel.org; Thu, 04 Nov 2021 14:24:28 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58432) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mihNx-0006hB-NT for qemu-devel@nongnu.org; Thu, 04 Nov 2021 14:22:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:57090) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mihNt-00005Z-Al for qemu-devel@nongnu.org; Thu, 04 Nov 2021 14:22:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1636050161; h=from:from:reply-to: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=t6yKkvNHhzIqS2xNPDmEQ99vXtTDaj8sPRBplTl5p4E=; b=YFjH4MbUWB0yDedWLKKGMe48r2uBiSVUozTsZN1pFk0lH4YW2Y+QjjLZtQ59/sPWHJTa2Y ryLdp4zMNOFLn+sIrfpwmHATEIbWxIfAzg2HhOHsp8cyiXnf11qt0vhyWTrb/+pp2vLY3+ Iz4bHRJ4BLMhypt6ClaJXay/A0xx7iM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-39-c55LYKpxMLW3633_TS-qFQ-1; Thu, 04 Nov 2021 14:22:37 -0400 X-MC-Unique: c55LYKpxMLW3633_TS-qFQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8BF8C1922023; Thu, 4 Nov 2021 18:22:35 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C3D7B1803D; Thu, 4 Nov 2021 18:22:28 +0000 (UTC) Date: Thu, 4 Nov 2021 18:22:26 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 1/3] sev/i386: Allow launching with -kernel if no OVMF hashes table found Message-ID: References: <20211101102136.1706421-1-dovmurik@linux.ibm.com> <20211101102136.1706421-2-dovmurik@linux.ibm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.648, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Tom Lendacky , Ashish Kalra , Brijesh Singh , Eduardo Habkost , James Bottomley , Marcelo Tosatti , qemu-devel@nongnu.org, Dov Murik , Tobin Feldman-Fitzthum , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Nov 04, 2021 at 06:18:10PM +0000, Dr. David Alan Gilbert wrote: > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > On Mon, Nov 01, 2021 at 10:21:34AM +0000, Dov Murik wrote: > > > Commit cff03145ed3c ("sev/i386: Introduce sev_add_kernel_loader_hashes > > > for measured linux boot", 2021-09-30) introduced measured direct boot > > > with -kernel, using an OVMF-designated hashes table which QEMU fills. > > > > > > However, if OVMF doesn't designate such an area, QEMU would completely > > > abort the VM launch. This breaks launching with -kernel using older > > > OVMF images which don't publish the SEV_HASH_TABLE_RV_GUID. > > > > > > Instead, just warn the user that -kernel was supplied by OVMF doesn't > > > specify the GUID for the hashes table. The following warning will be > > > displayed during VM launch: > > > > > > qemu-system-x86_64: warning: SEV: kernel specified but OVMF has no hash table guid > > > > > > Signed-off-by: Dov Murik > > > Reported-by: Tom Lendacky > > > --- > > > target/i386/sev.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/target/i386/sev.c b/target/i386/sev.c > > > index eede07f11d..682b8ccf6c 100644 > > > --- a/target/i386/sev.c > > > +++ b/target/i386/sev.c > > > @@ -1204,7 +1204,7 @@ bool sev_add_kernel_loader_hashes(SevKernelLoaderContext *ctx, Error **errp) > > > int aligned_len; > > > > > > if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) { > > > - error_setg(errp, "SEV: kernel specified but OVMF has no hash table guid"); > > > + warn_report("SEV: kernel specified but OVMF has no hash table guid"); > > > return false; > > > > I'm pretty wary of doing this kind of thing. > > > > If someone is using QEMU and they required to have the hashes populated > > for their use case, they now don't get a fatal error if something goes > > wrong with the process. This is bad as it hides a serious mistake. > > > > If someone is using QEMU and they don't require to have the hashes > > populated and they knowingly use a firmware that doesn't support > > this, they'll now get a irrelevant warning every time they boot > > QEMU. This is bad because IME users will file bugs complaining > > about this bogus warning. > > > > > > If we genuinely need to support both uses cases, then we should have > > an explicit command line flag to request the desired behaviour. > > > > This could be a -machine option to indicate that the hashes must > > be populated. > > > > - unset: try to populate hashes, *silently* ignore missing table > > in ovmf > > - set == on: try to populate hashes, report error on missing > > table in ovmf > > -set == off: never try to populate hashes, nor look for the > > table in ovmf > > Or as a property on the sev-guest object. Yep, I thought of that too, and I'm pretty undecided which is "best". -machine makes sense as 'kernel' and 'initrd' are properties of the '-machine' and we're doing stuff related to the. -object sev-guest makes sense as this is behaviour that's (currently) specific to SEV. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|