From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail02.groups.io (mail02.groups.io [66.175.222.108]) by spool.mail.gandi.net (Postfix) with ESMTPS id BB2F4740038 for ; Tue, 30 Jan 2024 11:39:01 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=yggo+iatpBuARWLyGWdm1JyWeweVdoGpMCbV6kC6oMw=; c=relaxed/simple; d=groups.io; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version:In-Reply-To:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Type:Content-Disposition; s=20140610; t=1706614740; v=1; b=Tyjgm2uIEqVHjcholnMgycGEalJw/+a8rmrHxNq7EYT/PqyOXSM8ACkZuEeNEjIO9KQs74LK +XM/Rr3YPN586piLqF4vwJebNtlimHyqRZJJHiwyRsWG2f/TZ+1LpZ4rGZyaWC6Qmf62KPLsx1x zaAB35vrXKAEC+JdH9HsWaKo= X-Received: by 127.0.0.2 with SMTP id 9bbkYY7687511xEvU2o5KemN; Tue, 30 Jan 2024 03:39:00 -0800 X-Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by mx.groups.io with SMTP id smtpd.web11.16112.1706614739819828899 for ; Tue, 30 Jan 2024 03:38:59 -0800 X-Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-317-pnDi_eO2MbWj9PLrFEVI4A-1; Tue, 30 Jan 2024 06:38:56 -0500 X-MC-Unique: pnDi_eO2MbWj9PLrFEVI4A-1 X-Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2582310A5CC6; Tue, 30 Jan 2024 11:38:56 +0000 (UTC) X-Received: from sirius.home.kraxel.org (unknown [10.39.192.180]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6B009A2E; Tue, 30 Jan 2024 11:38:55 +0000 (UTC) X-Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id 48DD5180038B; Tue, 30 Jan 2024 12:38:54 +0100 (CET) Date: Tue, 30 Jan 2024 12:38:54 +0100 From: "Gerd Hoffmann" To: Tom Lendacky Cc: devel@edk2.groups.io, Ard Biesheuvel , Erdem Aktas , Jiewen Yao , Laszlo Ersek , Liming Gao , Michael D Kinney , Min Xu , Zhiguang Liu , Rahul Kumar , Ray Ni , Michael Roth Subject: Re: [edk2-devel] [PATCH 15/16] Ovmfpkg/CcExitLib: Provide SVSM discovery support Message-ID: References: <74b31ae9-25a8-48c1-97c4-6fbea6e5bee3@amd.com> MIME-Version: 1.0 In-Reply-To: <74b31ae9-25a8-48c1-97c4-6fbea6e5bee3@amd.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,kraxel@redhat.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: X-Gm-Message-State: TtY3QXUUrKbm7Tm5vDLWOQolx7686176AA= Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=Tyjgm2uI; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=redhat.com (policy=none); spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io On Mon, Jan 29, 2024 at 12:04:51PM -0600, Tom Lendacky wrote: > On 1/29/24 09:23, Gerd Hoffmann via groups.io wrote: > > On Fri, Jan 26, 2024 at 04:13:14PM -0600, Tom Lendacky wrote: > > > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=4654 > > > > > > The SVSM specification documents an alternative method of discovery for > > > the SVSM using a reserved CPUID bit and a reserved MSR. > > > > > > For the CPUID support, the #VC handler of an SEV-SNP guest should modify > > > the returned value in the EAX register for the 0x8000001f CPUID function > > > by setting bit 28 when an SVSM is present. > > > > > > For the MSR support, new reserved MSR 0xc001f000 has been defined. A #VC > > > should be generated when accessing this MSR. The #VC handler is expected > > > to ignore writes to this MSR and return the physical calling area address > > > (CAA) on reads of this MSR. > > > > I'm wondering why this is handled by the ovmf #vc handler instead of the > > svsm #vc handler? > > OVMF will be running in guest VMPL1 context, not SVSM VMPL0 context, when > the CPUID instruction / MSR access is performed. In that case, it is the > guest VMPL1 #VC handler that will get control and have to respond. IIRC vmpl0 can handle #vc exceptions for vmpl1. But maybe only in case vmpl1 hasn't a #vc handler, i.e. vmpl1 can't cherry-pick which exceptions it handles itself and which it delegates to the SVSM. What happens once the linux kernel called ExitBootServices? Will the edk2 #vc handler stay alive? Or will the linux kernel install its own handler? take care, Gerd -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#114772): https://edk2.groups.io/g/devel/message/114772 Mute This Topic: https://groups.io/mt/103986477/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=-=-=-=-=-=-=-=-=-=-=-