From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from SJ2PR03CU001.outbound.protection.outlook.com (mail-westusazon11012016.outbound.protection.outlook.com [52.101.43.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2E49A2D97AB for ; Fri, 16 Jan 2026 10:14:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.43.16 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768558444; cv=fail; b=GKlQFyFcCP2Fiply2Li3bBDO4Okl+MlI1PobapV1e2Yj3IujtHdrkl1Fpg7/SDBAq/VVs3PHli8l2jqLZigAfcZZIebwsQHZDNuXo84XVTDk1MpwPAibOKQ7B67M6nHQsTN8hpR2UbwUVoglTr59EBPW6DdR4kw+4ThPVLrK9Cw= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768558444; c=relaxed/simple; bh=i8roLlEALXGw6emSFBWLT7FKDgVE0mDXQmwe0GP/P9E=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=sOxUAvXpU+PPtiOdunsQptco0iQ8Hn2CzHh4vC819eq6+fpoSL/KYsd+OsPoh/RsSAhXju1+FpxdRFMRa87p7DOUPcJhw3IFm7cqfWGYbCtlzSRwOmhU8Y6wqYeyv+nhrj1gSn7HImMEpgVm009ef0n1rCMgkRYabWvaQJRZIEY= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=citrix.com; spf=pass smtp.mailfrom=citrix.com; dkim=pass (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b=fUgtAcCo; arc=fail smtp.client-ip=52.101.43.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=citrix.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=citrix.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=citrix.com header.i=@citrix.com header.b="fUgtAcCo" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=ZL8ujIbw8rvewD7uIGUu1C7BIjwV/xAgO4zmzx1ATjxpcAGH7jfbmewxOZZeXA9KBHFVx2fYArasHa0qjB/E9G9UXhfD5yD599jKP/yp31ZLcYeORmDyUhfcOpjpfeijBtWsf6FMTEL8F28HynJ4qHerYEVRBrzKDhaJxwyormEOU/8K5+BH4m8b8PEM0kEHOpv+69Jk7amJTquiHwUd0lQUPJ8i5reAA/zFKh4NIw+Ewu6UOsHhX6pR4Wfwe13HfvrHElj9hHl6hEcyRNtj3J7D4f8xc4m8ZRZ5Z5a5edPVwt6F9q03kVsbsZU5qelvaVWC9SqHEut+2zHcL80GOg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=Cfo1hI8xy8/VI6oFbZTtvWoCByQsmpzqiTRbs7s8Rrw=; b=Z1c7A6g1X9OPGyG6k/e846x4cSQOp2Oaz7jyPOFd7H5nsh41XsJo6UJocHk0jAfTCWeWPV9ZkZ2UEHrI3xTDNR6u0VWMiuJ3fPW0Gt+OSDBYmCN8QspsmbchclOyKkcJrSdC4PGftG8g4eU5dxDNq+/aRIZciqHRj324KqtlCUw00PV3hYgV9k8mNyZIomTqpvB2IfdddijXBtgFDaglnL5rvqD93GKFXxQ+dKD8hgxALmfnTAMMQP3bDem1h1A3oISbT78pWRnXyLJUGFOtgcWKekOOsi+jdjfnn+XpYXiSVwL0LAr6V0E53NNWVBUcntHQQIPgs+K6DHALJXVpdg== 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.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=Cfo1hI8xy8/VI6oFbZTtvWoCByQsmpzqiTRbs7s8Rrw=; b=fUgtAcCoN6e9I65o04WsUWDwlPRXj+JkmEerkwoIr7O/y9HHhE3AOXEJWq039I58WI0btsY1ytDcZKUQ45nx8RtS2bhWu/xuGG4lpgHg++5K5iSJ4IXl1uA4nIGWxXPUz9jYA+S4DHGgC5468Fwm+l/QhL7mFJyS49MJ8r0hqAU= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=citrix.com; Received: from CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) by PH0PR03MB6870.namprd03.prod.outlook.com (2603:10b6:510:167::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9520.4; Fri, 16 Jan 2026 10:14:00 +0000 Received: from CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343]) by CH7PR03MB7860.namprd03.prod.outlook.com ([fe80::f5ba:35df:1c9f:b343%4]) with mapi id 15.20.9520.005; Fri, 16 Jan 2026 10:13:58 +0000 Date: Fri, 16 Jan 2026 11:13:55 +0100 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: James Dingwall Cc: linux-kernel@vger.kernel.org Subject: Re: xen pci passthrough stops working after xen/x86: fix initial memory balloon target Message-ID: References: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: MA2P292CA0016.ESPP292.PROD.OUTLOOK.COM (2603:10a6:250::14) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|PH0PR03MB6870:EE_ X-MS-Office365-Filtering-Correlation-Id: 0b1b3a90-f2e0-4ff0-a2d1-08de54e7f6a9 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016; X-Microsoft-Antispam-Message-Info: =?utf-8?B?U0h5ZVdXT0FGbWpSTWo0a0lJaVZqVzhIRk5iRWJ1azBKUkdKMVZpaGtzaFhu?= =?utf-8?B?OWNQVEJDSTR5SHR2UStNR01kdlN2MkJIYXJuNElYbW5nRUF1RURaazdBcTMw?= =?utf-8?B?bXl3VENRS3BDRk56WHc3bEVJOUUvMFZPMnhZaHRvRVVMVWNVbENTZ2c2aTVa?= =?utf-8?B?WGdNL1d5M3JSSGxKNGxmV0xmN3c2Q2hCVnA5TWRJOG1HTVhiN3V3bFZMY1Zo?= =?utf-8?B?b1A1ZkVQUC9iL2s3cGNwN2txdFBaUU1vQnNEdmsrMVFGS05JeXhNTTl4aEFF?= =?utf-8?B?SUsxVitOZzlkT1hkVFdrZG1qbzk0anhCYkdXelZtZ05Bazk2NmtNWXlzVlNa?= =?utf-8?B?NHp4OVNDbnBodW9Zd0dWMzYrZVhwbW1kdGFrSldIL3ZjTUkwN3A0dXFXb3Vs?= =?utf-8?B?cmZRSUM4ODM5dmZaeFhIQmsvOC9nSm1Hb2VCeElvcXlKUlFjZTA5N2hUalJv?= =?utf-8?B?V0Q5c1FJc3MrK2gzYitQb1N5VFRpTFRRbDhIVSt5WEIveG1pdmRnY3NOOFY2?= =?utf-8?B?b1Rqcm80RlN3a0cxOGo3QVNEcnlVd2F2VG5HRFB0d3lKV3N5SlhrR0hxTVVK?= =?utf-8?B?UDNndkxkTHZxaU5EeE9WNmMwU1c3bHIwQmJZMHV3REZ2NGNqUXg4MFhMU1Yr?= =?utf-8?B?dzE5SWpRTkE1WVlTZXkySGtCNmo2OUhsTVlBRm4yRkVvR1F3YlR6cGwzUm10?= =?utf-8?B?RGNvMEl2Tmd2eWYvdGY4ZzNDVTRUMVVsMXFNdEV1QjRWNFo3U3pEbzh3cEhl?= =?utf-8?B?OFF1YSs2KzlYSVdFUENxYys5T1JPY1Vlc1RKL1l5NXM1bG1wOS92ZDA0Ukh4?= =?utf-8?B?T1hDeTFGV1l6K1pYazhmc0xzUlRRUE1DZE9YcG00em1EVStmL3BGb1JvbGZ0?= =?utf-8?B?UHNZVkk1Zi96YkJoVDJpNGtUZkUvaTVRTEVDa0xDb2w0elgvci8zbE9mcmJm?= =?utf-8?B?cTNXTjI3d2o1Z0lXRlA1QjFZNGhma05idDljUGZyUGpUKzVVeElmNEorTmdw?= =?utf-8?B?Y0lmR3F1YTVXazNHeXpXT01yNEljUlBaVndpV0xTNW5sdDZrSzhZUFZ1MFhM?= =?utf-8?B?NWhxRWNZcVc5UkpyaW5WcEM4d1EyY3piTWtMUXBlVXY3VWNuSjA5RXl3RTE4?= =?utf-8?B?ZnJwNUFyeEdiR2N3VHpITEhiY28veFdJajhWWDNTc2doRlJ1eHNSYWl4ZDJp?= =?utf-8?B?UG1MZnQyOXBlL2Q2NnhnK3J5UnBIUmNlTmtSZWpSbjJRRlphV1FnRjlNQTdU?= =?utf-8?B?Z0xpOU83UG0wV1RmSGYyR0lUdExzOXQ5UENBM3VDT1hId1d2VHBlR1F5YjB2?= =?utf-8?B?OW9aeGVZOGhnOW1pZ1J0WlFDTTZiWlloRTljZFUvRVhSMmNmemtHZ0lFcUpk?= =?utf-8?B?eXBVV3MyRTh1OE5laXRsaEU2NDNlTDlOdkYyZVM1a2hxcE85djN6UFhoSG83?= =?utf-8?B?YVFhSzlwbXpKN0xrMnVyZEEycEpZZkx0NXFxNDZqd3FLdDkzU3YvOHFacUJT?= =?utf-8?B?Nlo2Skw0M1RXbTViak5Ub1NROVd0N0Y0c0YyVFQ5alF3VmgvdGE5dC9STGlG?= =?utf-8?B?R2RqaWRFcWIwZmVZWTJzRVVKNVhrZVVTMDk2bjRkMWdldUovZGV2V3hWbFRt?= =?utf-8?B?RkNueGN0V21qcWdUNzhRVFVQSkRVUnV3dkR5K2E4ZzJKZWwzU0FtbUdMOEsz?= =?utf-8?B?NnF2WHZHazJjcFNQVDdjVzYwNG1IUURRdTNLbEFMSk9kTS9Cb0ZBd21hSVFi?= =?utf-8?B?MW5lZWU5eFJlUEIzV3F3K2QwWHRwaW0yWGs4Q01KSk1uejNxVUtMTW9UbWlm?= =?utf-8?B?QVhNZVNuZlpwV2Izc2JYZTNFNmpnbUtjOFpVTENPSFZwaExLUHBvWXp5dmp4?= =?utf-8?B?MDNKV3NXR3JqMTlCOFpINXlRSTluMmFhNzB6OFg2a3FHNnFFeEdBQnA0S3Mv?= =?utf-8?B?QlloYmNXbVlvV1p5TTZ4V3NlZk15ZmRDcE11blVPUU01MlBXUWVXSndYeVll?= =?utf-8?B?OFhLYnpHREtJb1BmcGxxcFU3YkJOUjFTcWRxREZ5REtPUkhsYXZ2U3VQczFE?= =?utf-8?B?YUlkTjNzL0w5YUtqUVY0M3RFS0QrZWUzOFJiZVNkZEMvR3U0NkdsV0RpMWdt?= =?utf-8?Q?tvAI=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:CH7PR03MB7860.namprd03.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(376014)(366016);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?b2JUQm1CcURBa3ZCOC9vcm10dE9WU0M3dFRhSFlsdk5udy9YMFM4RzFQcFYz?= =?utf-8?B?ZDJmd0ZZWWZ1WWRLZVlSalM1YWx0aXdhVkE4bTZlSDRPQUJYU1RGcXlTaVNh?= =?utf-8?B?OG5PVkdOSFpmNklMR0Z1MVNJdVpETmVpMXNrQUFqRUlZUkF5c1BQVWNxcXlu?= =?utf-8?B?bXNlQ3RzdisrWFVXUGkzNklWOGc1cDZSZm02QVNXb1Y2cjc2L082MWIwcU5I?= =?utf-8?B?ODFIazhQTDQ1c1R0TktxbXEyZGt2dXZVN1U0UXdPWTRPWkdVNGM0VXBBNDNR?= =?utf-8?B?dG13NFpDZ084Zzc5WC9FR05UVlc5Qk9uUWxZNlhPN3F4aGtLTEZKNUtQaHB3?= =?utf-8?B?Smk2U2tJcWNpM0ZZOU04dEJ0a215UHRjcTZBalp4WkNNRzdvTXBscVlBSktn?= =?utf-8?B?clJkbmlCT2ZVT0tReG5KQzFtT0lWUzBWRlhLamZOWHZnTXp3Vm45U3NrY3Vs?= =?utf-8?B?SDVFRi9IVU8zVFp5dDFFcGZDWGNsTzJ0SFlWaHlFNGh3YUJ1cGdSWnpkOUFI?= =?utf-8?B?dDJDb0Myb0Z1U2hCa0pkWkVnL0JEMks4UGlBNi9TM21Ed2pPelhqNVlicjRT?= =?utf-8?B?VzFXZ1hmdEUydnZqcmRLbE04ekpySWFyeGFGSVlVQmxDbVhHV0pyUWIzdXJo?= =?utf-8?B?bnYrQTlTTktZWEdkbG1sVlluWkFCVUNabDEzQ3dNeDk4aGltQ3V6UnoyYlVs?= =?utf-8?B?T2ZtSkxIUXRudG1nVE5lVWlJaFRkYkR4MFhQakRhMzR5ZFJwTmtlakJuUEhk?= =?utf-8?B?aDg4MHUyOWxCcUxtZUtXVjF5Ly85R2dRajNKdGJUSmEzMi9QanpoOWVUOHlU?= =?utf-8?B?aWhsa285YlhZUjMwVmJoZytRelVieEhXZWRMTXBvNVJLY29ES2h3NDg4KzRC?= =?utf-8?B?dmdzZWQ1M1dFM0JVWnJnRVc5TkU2bVhqR1lvZ2c3Y3daT1NnQ3lTTGV4QWxK?= =?utf-8?B?MEVDVktzR2F5RW9kNUY5R0s4UitaenpRQzZ6NU9LSW9wc3hNK0pxUTVQZ0R1?= =?utf-8?B?ODdqOHZuUzYxbFpmZVBCeVdmcnhkSEZQbmN3RDQ3dm95bFBOVVdPd1krRTE1?= =?utf-8?B?SjVDdnhXNm5EU0V3d1BMZmdZaks2cGcyWDhrRjlFb0ZyUnFLWmwvd2IrTlFp?= =?utf-8?B?MVlRNTg4YUJtTTkxZTl4dzlLdzlrcmt4UDljNmt0UHNQUmVZR1BBZHA1K1hF?= =?utf-8?B?ZmNDWXMyaEZreldpTjNGZlVxTU0xek5yYk9pRm1mRUdKNThRUG9leHdmeXZl?= =?utf-8?B?ay9WeFB0bEw2aVZ1V3FUS3ZWYU9wdk8zbDVWQUV5M0lZem9iOUtPMzlvWnlL?= =?utf-8?B?anRCMnczNnhWK05Vdkk0RkxYSmN2VFpxSW54V3YwbVY1ek9qWHphNGlDdzZi?= =?utf-8?B?VlZ1dDNsdkVENXJYNWxPL2wrTTFnZVRrRVE3cVplNDdWd2N4eFJFYTc1bzVZ?= =?utf-8?B?dGpqZERKMy9xc2lXL1JyZlhmbUdyVU9sTnhpaFRyd29KOTJLcnpTTzlqaTdH?= =?utf-8?B?bDY4Y1ZTdWcyWWM0NmJMRjRZSjNncFpSb0xmQUxBVGQvdHhjb1NKODhVVHlD?= =?utf-8?B?S2h1a05DaWFKY0k1U0hYeFlqTEVBYnBLU3RUTGdtazhhOU8vWjdNNVR4Y3FF?= =?utf-8?B?S09NRVBuMlRhcG1Fbks4R1hVamZMYlBORkEyMFlzUUF6WXpxcmMxWjlMQW1D?= =?utf-8?B?T21LSTlIRTVNVnNSSGxMQm5lZUw0T3ZpU1kwRmxTdmxiclQ0RkxhWGRWdTdS?= =?utf-8?B?cXZab0NwY1ZoTitjN0RjYnh0NG53ZFlaUFRCUmFGb1FBemF6S09qeTZ1YS9l?= =?utf-8?B?dWpoVlhRVERxWVRLMXdIaWQzWkdsYW4vQm94RmI5ZGVXOUJIMDNSbGEwR055?= =?utf-8?B?bExHZ3l1ZzBHdWc2M0ZwOEJzdUVXMmdXb21vNHJubUlVOGdMdko3MmRIZ1lr?= =?utf-8?B?QzFoaVBLS01UNm4zL0l4K3VVWXdPeDc1eXo1Mm5hNm9EcFlTM0s2Z0VxcTla?= =?utf-8?B?VmlzQ0pLTGlCbWZOM2xQNlU4cUJpK1RvaFIrTVlTamw0YTNTcTI1Z25WSjA4?= =?utf-8?B?eGFoOTg4TUhZV0M5UXBLalZoMUdRVXVhd2RZU2RiLytwc3NGajJMbnl0a0dL?= =?utf-8?B?MlB2SGRvMVR3dm9XQW1NZW1pd0pQUk4yS1l1UjJTSUVyTk83MjVlaW1ESzBK?= =?utf-8?B?ZlBhUjc1SlU0WS9lZTlOeU41TzFheXNEUjF6RlZYd1N6Zy8zVnBoVEVMRjQy?= =?utf-8?B?RXI1TWdtRkZYWnlKdTBENDJ3clBTMWF1UVNkQlJaclgxMEpaMk1xaTd0ZmUz?= =?utf-8?B?L0x3QTQrVWM2ZzNHOFQrb0RBbzFKeTIyYnBnYzRraXFiTnNCVU1Gdz09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 0b1b3a90-f2e0-4ff0-a2d1-08de54e7f6a9 X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jan 2026 10:13:58.7895 (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: SRkDwrA7isfZ4HUUDymcHmZnQYYimLtxQXY2BhQ2LIxE/gATYVhUU8xiz248gVKbfQ9urgAEAKkiXnZ875mHxg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR03MB6870 On Fri, Jan 16, 2026 at 09:27:15AM +0000, James Dingwall wrote: > On Thu, Jan 15, 2026 at 06:55:15PM +0100, Roger Pau Monné wrote: > > On Thu, Jan 15, 2026 at 02:50:12PM +0000, James Dingwall wrote: > > > On Thu, Jan 15, 2026 at 01:03:49PM +0100, Roger Pau Monné wrote: > > > > On Thu, Jan 15, 2026 at 11:23:37AM +0000, James Dingwall wrote: > > > > > Hi, > > > > > > > > > > We have encountered a regression with pci passthrough since the > > > > > Ubuntu 6.8.0-91.92 which included this commit: > > > > > > > > Hello, > > > > > > > > Thanks for the report. Could you also send me your kernel Kconfig, to > > > > see which combination of options are you using? > > > > > > > > > Can you confirm that the config used to build the non-working kernel > > also has CONFIG_XEN_UNPOPULATED_ALLOC=y? > > The config is the same for both builds and CONFIG_XEN_UNPOPULATED_ALLOC=y > is always set. > > > Can you also provide the output of `cat /proc/iomem` for both the > > working and non-working kernels? > > non-working Ubuntu-6.8.0-100.100: > > 00000000-00000fff : Reserved > 00001000-0009ffff : System RAM > 000a0000-000fffff : Reserved > 000f0000-000fffff : System ROM > 00100000-2007ffff : System RAM > 01000000-025fffff : Kernel code > 02600000-033bcfff : Kernel rodata > 03400000-0385613f : Kernel data > 03d54000-041fffff : Kernel bss > 20081000-73b57fff : Unusable memory > 76c58000-76d76fff : ACPI Tables > 76d77000-76ea0fff : ACPI Non-volatile Storage > 77fff000-77ffffff : Unusable memory > 80000000-87ffffff : System RAM > 88000000-8fffffff : Xen scratch > 100000000-103f7ffff : System RAM > 4000200000-400021ffff : 0000:01:00.0 > 4000220000-400023ffff : 0000:01:00.0 > 4000240000-400025ffff : 0000:01:00.1 > 4000260000-400027ffff : 0000:01:00.1 > > > working Ubuntu-6.8.0-100.100: > > 00000000-00000fff : Reserved > 00001000-0009ffff : System RAM > 000a0000-000fffff : Reserved > 000f0000-000fffff : System ROM > 00100000-2007ffff : System RAM > 01000000-025fffff : Kernel code > 02600000-033bcfff : Kernel rodata > 03400000-0385613f : Kernel data > 03d54000-041fffff : Kernel bss > 20081000-73b57fff : Unusable memory > 76c58000-76d76fff : ACPI Tables > 76d77000-76ea0fff : ACPI Non-volatile Storage > 77fff000-77ffffff : Unusable memory > 81100000-811fffff : 0000:01:00.1 > 81100000-811fffff : igb > 81200000-812fffff : 0000:01:00.0 > 81200000-812fffff : igb > 81300000-8137ffff : 0000:01:00.1 > 81380000-813fffff : 0000:01:00.0 > 81400000-81403fff : 0000:01:00.1 > 81400000-81403fff : igb > 81404000-81407fff : 0000:01:00.0 > 81404000-81407fff : igb > 81500000-815fffff : 0000:03:00.0 > 81600000-816fffff : 0000:03:00.0 > 81600000-816fffff : igc > 81700000-81703fff : 0000:03:00.0 > 81700000-81703fff : igc > 88000000-8fffffff : Xen scratch > 100000000-103f7ffff : System RAM > 4000200000-400021ffff : 0000:01:00.0 > 4000220000-400023ffff : 0000:01:00.0 > 4000240000-400025ffff : 0000:01:00.1 > 4000260000-400027ffff : 0000:01:00.1 For some reason (which I still haven't figure out), the fictitious PFN memory layout created by Linux ends up placing a RAM region over the BAR MMIO space used by igc, the difference: 81200000-812fffff : 0000:01:00.0 81200000-812fffff : igb 81300000-8137ffff : 0000:01:00.1 81380000-813fffff : 0000:01:00.0 81400000-81403fff : 0000:01:00.1 81400000-81403fff : igb 81404000-81407fff : 0000:01:00.0 81404000-81407fff : igb 81500000-815fffff : 0000:03:00.0 81600000-816fffff : 0000:03:00.0 81600000-816fffff : igc 81700000-81703fff : 0000:03:00.0 81700000-81703fff : igc 88000000-8fffffff : Xen scratch 100000000-103f7ffff : System RAM VS 80000000-87ffffff : System RAM 88000000-8fffffff : Xen scratch 100000000-103f7ffff : System RAM In the non-working case there's a chunk of RAM in the space that covers the device MMIO BARs. I fear my balloon accounting "fix" has instead introduced a miss accounting in the balloon driver that causes Linux to attempt to balloon up memory and it ends up instantiating a hotplug memory region over the device MMIO BARs. I'm still confused as to how the change in balloon_add_regions() has an effect when CONFIG_XEN_UNPOPULATED_ALLOC=y, as it should become a no-op in that case, but I will debug this myself. > > Just for completeness the working build also reverts "xen/x86: fix initial > memory balloon target" because of a conflict in drivers/xen/balloon.c. Hm, but that's the same commit that you mentioned in the first email, there you said reverting: commit 74287971dbb3fe322bb316afd9e7fb5807e23bee Author: Roger Pau Monne Date: Wed May 14 10:04:26 2025 +0200 xen/x86: fix initial memory balloon target Fixes the issue. Is there an additional commit that also needs reverting to fix the issue? That would make more sense, as IMO that commit should be a no-op given your Kconfig. I don't think I will be able to get into this until Monday, sorry. In the meantime, does disabling the balloon driver mitigate the issue? Thanks, Roger.