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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 CEB28C433EF for ; Tue, 14 Sep 2021 16:28:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A1BA0610F9 for ; Tue, 14 Sep 2021 16:28:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229610AbhINQ3X (ORCPT ); Tue, 14 Sep 2021 12:29:23 -0400 Received: from esa3.hc3370-68.iphmx.com ([216.71.145.155]:64854 "EHLO esa3.hc3370-68.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhINQ3W (ORCPT ); Tue, 14 Sep 2021 12:29:22 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1631636885; h=date:from:to:cc:subject:message-id:references: content-transfer-encoding:in-reply-to:mime-version; bh=0oDu8A4E1nBudlkblNkn/OQ6raVkygEBFAyYDouYCeE=; b=dJD9VqYZJsz+DEu31N5FOZQPscz1Zz+Dr76wqPE9JXIGevLhtzW+NlPE /IFtcWw5xoPxIWr8ljdTXa3U9Mpln6ZBJVH7QomhjxoK0YvEojhEFFZ4N bMeGq4hzP/m5cIfws/i2a9dHyVVeZF/qCNcIm62HjQcdbDyqro5wAT6UW Q=; Authentication-Results: esa3.hc3370-68.iphmx.com; dkim=pass (signature verified) header.i=@citrix.onmicrosoft.com IronPort-SDR: sTpUpzu+P8oaQRNY5oXHzA/ElGr3kPGrlXi84A4uofqfk6PPHYpYRY7ciF7GoNVfqz+Z1L6hmw VA1YjAxELHjmcmVbt6UXOHEGm+2aA6uMndc/v9lBuB66SS65ASavL6xJzznfdLiDJtjx7tJaTn WO0qYQaMVSv+oRLdL8yIxXTySoYjLDxGJ1T/9xFX2zWNG/515XaacX6oylv+o763LOUhi9KcMC EzfYoGoBKRUaWBGkNyW/kl0I0BR+l3wd2WUVEhfMLCOPd6InzZfzTf5ejiNUtktPik7scXSyrO FXsLZebhKJQw2kJigpir6FsL X-SBRS: 5.1 X-MesageID: 52717053 X-Ironport-Server: esa3.hc3370-68.iphmx.com X-Remote-IP: 162.221.156.83 X-Policy: $RELAYED IronPort-Data: A9a23:xFRCm6JbAf6ysWIsFE+RRpIlxSXFcZb7ZxGr2PjKsXjdYENS0TYAy WYWUGiGOv3ZYDf3L9pzbNvn90oH75LTnNBiTARlqX01Q3x08seUXt7xwmUcns+xwm8vaGo9s q3yv/GZdJhcokcxIn5BC5C5xZVG/fjgqoHUVaiUZ0ideSc+EH140UM6x7Zj6mJVqYPR7z2l6 IuaT/L3YDdJ6xYsWo7Dw/vewP/HlK2aVAIw5jTSV9gS1LPtvyB94KYkDbOwNxPFrrx8RYZWc QphIIaRpQs19z91Yj+sfy2SnkciGtY+NiDW4pZatjTLbrGvaUXe345iXMfwZ3u7hB2kwvdPl dtg6qbpF18uBrfQxroEWkRHRnQW0a1uoNcrIFC6uM2XiUbHb2Ht07NlC0Re0Y8wo7gtRzsUr LpBdW5LPkvra+GemdpXTsF2gcsuNo/zNZ43sXB81zDJS/0hRPgvRo2Xv4ABg29t3aiiG970Q vsgMjxGYCjcICRSYFUuFpsYpcKn0yyXnzpw9wvO+PtfD3Lo5BdqzLHnPd7Re9qLbcZYhECVo iTB5WuRKhUbMsGPjDmI6HShgsfRki7hHoEfDru18rhtmlL77nweDlgaWEW2pdG9i1WiQJRPJ koM4C0soKMuskuxQbHVXRe1vXqFtR40QMdLHqsx7wTl4qjb+QGCHUAfUyVMLtchsaceTzsw1 0TPmMj1Hztxq76EYXWH/7yQoHW5Pi19EIMZTXZaF01fuYCl+dxtyEKUJjp+LEKrpvCoPg+tz R3VlnFg37Irl9JVibyyoE+S1lpAuaP1oh4JChT/Bzz+t14oO9H7PuRE+nCAsq0Rd9/xok2p+ SFewpnAtrhm4YSlyXTVKNjhCo1F8Bps3Nf0uldpA5Bp3DCk4XfLkWt4sWwmeRsB3irpf1bUj K7vVeF5v8Q70JiCN/Yfj2eN5yICl/aI+TPNDKy8Uza2SsItHDJrBQk3DaJq44wIrKTKuftuU Xt8WZ33ZUv29Iw9lGbmLwvj+eZzm0jSOl8/tbiklk/6gNJylVa+SKsfMUvmUwzKxPrf+23oH yJkH5LSkX13CbSmCgGOqNJ7BQ1afBATWMGtw+QKJ7HrH+aTMDx4YxMn6eh6ININcmU8vrqgw 0xRrWcDlAOk1CGYcF7TAp2hAZu2NatCQbsAFXVEFX6j2mQ5YJbp66EadpAteqIg+vAlxvlxJ 8Tpse3cahiWYjiYqTkbc7fnq4luKEaiiQ6UZnL3azkjZZ9wAQfO/4a8LAfo8SAPCAuxtNc// OL8hl+KH8JbSlQwFtvSZdKu00i14SoXltVtUhaaOdJUYkjtrtRncnSjkv8tLsgQAhzf3T/Gh R2OCBIVqLCV8Y84+dXEn46eqIKtH7csF0ZWBTCDv723KTPb7iyoxooZCLSEejXUVWXV/qS+Z LoKk6GgYaNfxFsT6thyCbdmy6469uDDnb4Cw1Q2BmjPYnSqFqhkfiuM0/5Qu/Af3bReowa3B B6Co4EIJbWTNcr5O1cNPw55PP+b3PQZlzSOv/Q4JEL2uH1+8LadCBgAOhCNjGpWLadvMZNjy uAk4ZZE5wu6gxssE9CHkiELqDjcci1eC/0q5sMAHYvmqgs30VUTM5XTBxj/7IyLd9gRYFIhJ SWZhfaairlRrqYYn6HfyZQZMTJhuKkz IronPort-HdrOrdr: A9a23:Mb7tLKkYhYJRdnw8k13bjLfa11rpDfIi3DAbv31ZSRFFG/Fw9v rDoB1/73TJYVkqN03I9ervBEDjexPhHO9OgLX5VI3KNGOKhILCFvAA0WKN+UyEJwTOssJbyK d8Y+xfJbTLfDxHZB/BkWuFL+o= X-IronPort-AV: E=Sophos;i="5.85,292,1624334400"; d="scan'208";a="52717053" ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=LR+UjHDak1cqYTDLICD7KCXbaMD+tUGN2bO0ZU0HScW5bizOffYJtDwIvAKscoBrBPL/XNZrvOR8fsWhNAhGgSnCjjQISTWagZKR0aIi2Bx2q2QUA5VO7KnF4xAdhiFvG5TvYXjB9ajnpTknvZ3MmEbma0Dvi9esf8MC723H0tFW47wtdJGm58pvC/0a8hd5xRP6Qb1J1C74blZ0LJ2+EFDepOvUBYGQjaB3lqpTup28L1E4xtZCeAJnJ0HUP8qR/3sbpTayeAy/ea22e3SJ10LvTRCruCIWgwvqdiN4LDsVbJNsYmGEEQlbB+3ko6AHc8kEuh8jf5GBJqxV0llCGw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=/FUPmgE0iKT7YxUURvlZlq/MtNcRKfBk8QhYO56li0I=; b=Oih5P4AE+atSEkVprqyWU7MDlGbx8Wp7CZG4u3HibtR78LpTjcfafewYKJck4vq4QaGfsmtPauzknUCXYAPlU7Jq9NnoWMdC3BYdQ9LJ6+N2mxuTSrWG1dlr61J6kk5num02a5qt07vKWPV10HH2WPmPpdIciBXP7M/AQF6Hbsrw53TIsogTm0qQWdIVgLCrdxi1jMV2LUHunKfftSgmCmMtuuczQM9+1yMgYLTtaTbQRrb9eTYAi+DRJqShwzN6L+L0yistVvMsXDGMm+RXKTIoGSROzlKBXWnwlFQnv7zSFg+NFYRYQ44n+pJy2bSzUgBh0VpbwJKRsUZGqiOrVA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=/FUPmgE0iKT7YxUURvlZlq/MtNcRKfBk8QhYO56li0I=; b=lVmHx1AUwybUpn2L10TQ4TTOMA5p9+kgoCaeGvo36TprCb0DfyAgRy0OWQonxQuBklr7ZKp2j0ZlgO5b8zVZ/X+nNp56kRTTjjfc2JKiKn5X9Srw8Fa+OZPKrlFiTEDal4D+UQPGvGKS7lsCG8wdC8l30hY8Cd5HOIaR8U4ITQY= Date: Tue, 14 Sep 2021 18:27:51 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich CC: Juergen Gross , Boris Ostrovsky , Stefano Stabellini , lkml , "xen-devel@lists.xenproject.org" Subject: Re: [PATCH 0/9] xen/x86: PVH Dom0 fixes and fallout adjustments Message-ID: References: <4efa804e-3250-227f-00c7-347581366cd4@suse.com> <050f71c8-227f-4f78-1ec5-394ba9fba9c1@suse.com> <40ea4ec8-483b-9191-a233-f2916f22c131@suse.com> <13dd8509-330b-4571-086a-7a3ed9c22c82@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <13dd8509-330b-4571-086a-7a3ed9c22c82@suse.com> X-ClientProxiedBy: LO2P265CA0316.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:a4::16) To DS7PR03MB5608.namprd03.prod.outlook.com (2603:10b6:5:2c9::18) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 5f5cc8a3-6cff-4a90-9cf4-08d9779c9be0 X-MS-TrafficTypeDiagnostic: DM5PR03MB2844: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:10000; X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: v76C3P8DenRctbHtidp9JEWnr81wtHuRBu/paS4bPExq75RpA3AwoLBu5yXgDOrPgMsVApa71R0IVofTGmjBgcOFxOs4hQF51G5oYry9wGWvADLfx0iC4SS/FCkRq89w5EsEIKt3ryYRZREC/tIdbQi4m5dQmF2PlTS2MEy4TJAoq4sHYxDifGisy2KN1Clvi2XODAsxJXNJ92p/9IqCq/soPEVSWDzcVVWsGAJDd6PTF9YneLCMUwOKUEv74ZoMZiOAh+QdmeYfjnvVYXgeyOYRPBDskDQnto0JhAgz+SVM07MTST4BPNrLRxyHIeoZXUAZ6lwOgK/3/GLENZ+vd4LAWQAxvUMav0KdArj80CS7kNi+XzTRLzCtSm/96M7xFEzkgBcEXwpvnLQWcSNFsHMVfQAb+SZKfoJ753AOTp4YyGOzG6kQ8QH1DHqZbV2zfqZwQEzPjrXDswmhWAf3OfXSsQomLQMRcJSPo7MRPQ6NAtzWU71dIFG6/9Kyo6ZJFSeNZqNmDuXIPtSRyIbvy053+HoGEu9R5Ww9lMTdIMjIZs0jyZ4YqcojqmEbgZEVVNWUti73U3V5Pz9BT+lhhjI8MeM+W6O1+N4tHDfNhDs0IPdApSUbNHa4sYjBZ1lLAxdCqIgxtC8fIyW8W0M7/g== X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR03MB5608.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(4636009)(396003)(376002)(366004)(136003)(39860400002)(346002)(85182001)(478600001)(83380400001)(5660300002)(6486002)(8676002)(4326008)(53546011)(54906003)(66946007)(956004)(2906002)(186003)(26005)(38100700002)(66556008)(66476007)(9686003)(86362001)(8936002)(6916009)(316002)(6496006)(6666004);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?aFBOWlVLcXBIa3d0MWVaSzc3Z0xTenh6T3NkUlNTajlWclNRZjRRdk84ckhM?= =?utf-8?B?c01WaUdrb0oxdGk1TUpaM2Jka21zUW9mTlQxWGdlZy9QTmhKWlI0RE9vTThK?= =?utf-8?B?bTFpQjFuTjJRL0dORndOdmtFV0txRGZkMnRicTR6Qk5yYTNsR2lMZlQ4SFZv?= =?utf-8?B?ZEEwbHBEa0xTSHdTSkFvUEttN2NQUFVqQWZmWGlhMnNGbjZsNSs3d3ArZlpt?= =?utf-8?B?V09QTW11VG5XNUZBTGE0M29OaTd1UWVSaFFzT2VtYmozQnNLY0srVFpSMFpU?= =?utf-8?B?aG9TQklKRDA3RjFiZ1ZKcG5XeGxBNmhZejkwUUo0SW5URzRoZ013OGIzMWI2?= =?utf-8?B?dnROZDJxN2V2T0s5d0U3S0pJb1pVYzcwSzYveTRUejJ5bHhQcWNOTnNLUGRP?= =?utf-8?B?R1NJU1VnSm9TMmxMekpDWWhZaVR3NmVBTmF3cUkrOVY0ZFN1eUpOYjdTa3Bp?= =?utf-8?B?ZGxZT3Z1YlZqUXdJWi9IZUIzSUJJZG1tcUl2YTA3Vm5Ub1hybWJMeDhsMmdJ?= =?utf-8?B?U1N0K1NSWlNYVm15Z0ViUWxYVDc0RGFGQmgxUndETC95U1Z5Zy9CRTBuTmU5?= =?utf-8?B?SnQraklkQTVtQVIvaHJlUXh4T2EwOUJRUDFIREttNnp1Y2drVGdIU3VsZjNa?= =?utf-8?B?RGFvM2NPT05YZ3VHSmloUHgzQkpXZUw4a1JwL0w5K1llMENOUkt2ZDJkcCtP?= =?utf-8?B?emFweFRadEV0Y3d2UU10Q093OG9YdG1pTDVVYThNTG1QRFVXOXVYVnkzZnNB?= =?utf-8?B?bWtlQ2RIem9TdnpyM0Z5NzN5OGlZeS9EYThXeVZ1dm10TVJEYmcxSzJzSld4?= =?utf-8?B?bi9KWkhQejRUNHk1dTlFVGVnUWplY3dVaXBmaUh6YkhRNUhBRGVZUmxRU0VF?= =?utf-8?B?QzJ1STBFUnJJbUUzUGZycXhDTzN3dzVGdEJqd1duZ1p2bkNTK3RHUENNU2xt?= =?utf-8?B?aVZTTWszSEpERkZad0tNaGJtaXhxOVQ1MmU5RWJyMCtxdVplZUFmQXIyVmtG?= =?utf-8?B?NDNnWnhJVG1sQUxWZGNvYUJ1aE5YV0VqbzFXR0NITEZVWnBkOGtBVk52UU5z?= =?utf-8?B?ekFVMkx6U3p5ekV2YWtHZ285T1pGZDdIdXBnYmpINnNTN2VnRzU4Mks1RnRt?= =?utf-8?B?dEU3SjUvc3ltYzZqeE9YTDJYZVN3azZVTTErcDk0RHhNUmpXaVJCdFA5VmJa?= =?utf-8?B?UXdrdnYwNTRqR2h3a2w2RCtSb3BNZ0M2U1Mrc0g1TjJVcUwydmIvMlhuaWlU?= =?utf-8?B?VWx6bGpURVN4bGNhRmVsN2R6c3ZFUFNrNXJ3WDNBdDdaMkxZNHhKMm5mMHhi?= =?utf-8?B?SGRkUVcvMlNNckNpYjdaejFMNDV3OEdFYmVpRUcvajRUVlFrMDN1bHlnczNa?= =?utf-8?B?WlJuVXcwTWN4NjdKS0RtdE5GZlpwRlZkODdMbjFXQ0ptR1kyY3pNbFd4OTJX?= =?utf-8?B?MmhSLzFDL3NCazdYaWgwZjhKT2RNeE0rbTNXU05OcFVlbkg2NVdrcjFReWxu?= =?utf-8?B?cFpLWDIreVFUMXlNdnEvOVdDYk80QlFoS1VmS01UNUJqbjlEbWxmb0hDVEVE?= =?utf-8?B?R1BPcjNJN1h4dGc2WHZ0bzFCRzZ6MW45Y1pYcFF0bDl2Y0pNQjlBeHpKWGJS?= =?utf-8?B?WS83YjVLQ3cvTGxiWkQ5dnVHK2M5b0ZZR0cxNG1tblZ0dFlCNVpWaEN1c29j?= =?utf-8?B?U1dMM2UraGwyaXVwalNWL3JXOFcrc24xUE9GVHhUY3Y0blo3VFJqVWtrTXNh?= =?utf-8?Q?Ad8XJ8sL/l34ys4acnUZvt5TKgzSLSIO3zEzvTq?= X-MS-Exchange-CrossTenant-Network-Message-Id: 5f5cc8a3-6cff-4a90-9cf4-08d9779c9be0 X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Sep 2021 16:27:56.5260 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: KDf2PF6qnty9LloXnEYG65aUYSZRufH+U9ObhYAJZx5kfHRm8cAIcdAALmMJ7wm34fCi3MJJ6zjr6KMb79Xj8g== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR03MB2844 X-OriginatorOrg: citrix.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 14, 2021 at 05:13:52PM +0200, Jan Beulich wrote: > On 14.09.2021 14:41, Roger Pau Monné wrote: > > On Tue, Sep 14, 2021 at 01:58:29PM +0200, Jan Beulich wrote: > >> On 14.09.2021 13:15, Roger Pau Monné wrote: > >>> On Tue, Sep 14, 2021 at 11:03:23AM +0200, Jan Beulich wrote: > >>>> On 14.09.2021 10:32, Roger Pau Monné wrote: > >>>>> On Tue, Sep 07, 2021 at 12:04:34PM +0200, Jan Beulich wrote: > >>>>>> 2) Dom0, unlike in the PV case, cannot access the screen (to use as a > >>>>>> console) when in a non-default mode (i.e. not 80x25 text), as the > >>>>>> necessary information (in particular about VESA-bases LFB modes) is > >>>>>> not communicated. On the hypervisor side this looks like deliberate > >>>>>> behavior, but it is unclear to me what the intentions were towards > >>>>>> an alternative model. (X may be able to access the screen depending > >>>>>> on whether it has a suitable driver besides the presently unusable > >>>>>> /dev/fb based one.) > >>>>> > >>>>> I had to admit most of my boxes are headless servers, albeit I have > >>>>> one NUC I can use to test gfx stuff, so I don't really use gfx output > >>>>> with Xen. > >>>>> > >>>>> As I understand such information is fetched from the BIOS and passed > >>>>> into Xen, which should then hand it over to the dom0 kernel? > >>>> > >>>> That's how PV Dom0 learns of the information, yes. See > >>>> fill_console_start_info(). (I'm in the process of eliminating the > >>>> need for some of the "fetch from BIOS" in Xen right now, but that's > >>>> not going to get us as far as being able to delete that code, no > >>>> matter how much in particular Andrew would like that to happen.) > >>>> > >>>>> I guess the only way for Linux dom0 kernel to fetch that information > >>>>> would be to emulate the BIOS or drop into realmode and issue the BIOS > >>>>> calls? > >>>> > >>>> Native Linux gets this information passed from the boot loader, I think > >>>> (except in the EFI case, as per below). > >>>> > >>>>> Is that an issue on UEFI also, or there dom0 can fetch the framebuffer > >>>>> info using the PV EFI interface? > >>>> > >>>> There it's EFI boot services functions which can be invoked before > >>>> leaving boot services (in the native case). Aiui the PVH entry point > >>>> lives logically past any EFI boot services interaction, and hence > >>>> using them is not an option (if there was EFI firmware present in Dom0 > >>>> in the first place, which I consider difficult all by itself - this > >>>> can't be the physical system's firmware, but I also don't see where > >>>> virtual firmware would be taken from). > >>>> > >>>> There is no PV EFI interface to obtain video information. With the > >>>> needed information getting passed via start_info, PV has no need for > >>>> such, and I would be hesitant to add a fundamentally redundant > >>>> interface for PVH. The more that the information needed isn't EFI- > >>>> specific at all. > >>> > >>> I think our only option is to expand the HVM start info information to > >>> convey that data from Xen into dom0. > >> > >> PHV doesn't use the ordinary start_info, does it? > > > > No, it's HVM start info as described in: > > > > xen/include/public/arch-x86/hvm/start_info.h > > > > We have already extended it once to add a memory map, we could extend > > it another time to add the video information. > > Okay, I'll try to make a(nother) patch along these lines. Since there's > a DomU counterpart in PV's start_info - where does that information get > passed for PVH? (I'm mainly wondering whether there's another approach > to consider.) We don't pass the video information at all for PVH, neither in domU or dom0 modes if that's what you mean. Not sure what video information we could pass for domU anyway, as that would be a PV framebuffer that would need setup ATM. Maybe we could at some point provide some kind of emulated or passed through card. The information contained in start_info that's needed for PVH is passed using hvm params, just like it's done for plain HVM guests. We could pass the video information in a hvm param I guess, but it would require stealing guest memory to store it (and mark as reserved in the memory map). Not sure that's better than expanding HVM start info. Maybe there's another hypercall interface I'm missing we could use to propagate that information to dom0? Thanks, Roger.