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 8A5B6C282EC for ; Thu, 13 Mar 2025 15:40:17 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tskfB-0004wl-Pb; Thu, 13 Mar 2025 11:40:01 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1tskf9-0004wI-6G for qemu-devel@nongnu.org; Thu, 13 Mar 2025 11:39:59 -0400 Received: from mail.8bytes.org ([85.214.250.239]) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1tskf7-0004aI-Hy for qemu-devel@nongnu.org; Thu, 13 Mar 2025 11:39:58 -0400 Received: from 8bytes.org (p4ffe03ae.dip0.t-ipconnect.de [79.254.3.174]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mail.8bytes.org (Postfix) with ESMTPSA id 119D14550C; Thu, 13 Mar 2025 16:39:55 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=8bytes.org; s=default; t=1741880395; bh=/1trWfMSL3RwQVf9Fp4HqMBC31Nmb8n71JNlDfGwX/Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=lk2X8zTspJ23ZUHnAO9MSqwldBnBdPAvaFzQ5e8YhnixyFqxMxBbbhwb193Og1pPJ Vi9CeB5aCSmYw+OXPoJkHw8I9L+eiSkCaUhFcn/2TlBqvNufqyfIy8UEbI5xTcVvQY 2aQzuaWdoZAI5sydUuzvpkpHLdF4RiySV95aalbKYu3ZEebA35UEJyDPSuZsNjcLkk wd8Vgv4TCLmwUcF6qZTsc4oO5bxzRZlwlPhJf1xxVmDxNyakkpDw9ispu887bAbYoY Zd0WgiEB9agXCykVtxf0Z4DqzllbKI2HNKN6/CVQF42iMZsN+8WKIFYJq/ac84XGiW Pq9YTf4SnVBqg== Date: Thu, 13 Mar 2025 16:39:53 +0100 From: =?iso-8859-1?Q?J=F6rg_R=F6del?= To: Ani Sinha Cc: Alex Graf , Paolo Bonzini , Eduardo Habkost , Marcel Apfelbaum , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Yanan Wang , Zhao Liu , Richard Henderson , "Michael S. Tsirkin" , Fabiano Rosas , Laurent Vivier , Gerd Hoffman , Igor Mammedov , Vitaly Kuznetsov , qemu-devel@nongnu.org Subject: Re: [PATCH v6] hw/misc/vmfwupdate: Introduce hypervisor fw-cfg interface support Message-ID: References: <20250214153443.159889-1-anisinha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=85.214.250.239; envelope-from=joro@8bytes.org; helo=mail.8bytes.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=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: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Mar 13, 2025 at 08:23:44PM +0530, Ani Sinha wrote: > Note that even with this approach where the hypervisor *thinks* it's > dealing with a real firmware, you can imagine a small rust based > firmware image that is loaded by the guest in the firmware region. > This tiny firmware then jumps to a well known address (chosen by the > guest) where IGVM is loaded and then starts executing the IGVM > instructions. Yes, but this way the predictable launch measurement property of IGVM is lost, as the measurement only contains hashes for the actions which happened before the VM was finalized and launched by the VMM. The SEV policy can also not be changed anymore when the guest is running. Anyway, I think it doesn't matter much whether the IGVM is parsed in guest context or by QEMU, as long as the resulting measurement is the same as if the file was loaded at initial VM launch. Given that QEMU will hopefully get IGVM backend support soon, there is some value and saved effort in just passing the IGVM data to the VMM via the vmfwupdate interface and let QEMU do the rest. Regards, Joerg