From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from NAM10-DM6-obe.outbound.protection.outlook.com (mail-dm6nam10on2083.outbound.protection.outlook.com [40.107.93.83]) (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 D6C0F2C158E for ; Wed, 16 Jul 2025 09:46:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.93.83 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752659208; cv=fail; b=KhmaNd6/UaGLoHlM1/8A7InPU7r0AZgGidp5Xjd2JbTZymrMwuj1k5U64u6NvrgfScYkQIQFavXHYPqdhP9eqUSmWtGku21RypQ/NVPkjtjR9V68jQb5NRT22K1j8C7tVoEFYoG0mQ7OhGyqkaqV7Nq1oZeFUYVxRLC1OPOpkC0= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752659208; c=relaxed/simple; bh=DUUMGcP8tHF244OgKncK6eCJmKLKQyItxJ2OhCgolyA=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=DpWP5YU8TJISBdg83k7UFA2+vn5q6cNqnbnpldSCgRusuCcb9oWN+1qg8fyfMVXclzNxFafQevxlnQrSz/AxGIAuzwBjM0/M+mYOl+tqJL1/60dv4BZxB0a5PpLyOpmnf6J5q6fzsomIyJBbxnNRd5tRQQoKqgO5QR4cnNRLiIA= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=vB39Rkcx; arc=fail smtp.client-ip=40.107.93.83 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="vB39Rkcx" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=U89Bn9B0EqejSGDkJIUglr34RZ/d737Jffu9h/7PQ96YmsXa5bGL2pcJWj3VLcmMe69A2UuRABwzgfIh0xoa57/30JnD5o84Qx4SU6WjRCKGKweQR4b2IZs0dyd7TivsHDnXRoRwqbLfbHA/NqqqnNXwB+23VOp+tsdetIxQ05GpzKBSOYrzVbLE3aBn6NC7RvA42Vo4EuAa0GOuzmCwW9QL61YNjUgvRjqNZMqOvfdA30CCG2Na6RSVWDkArjNE+QCotLVtGHkm61QidJrQBNaVMaLa1BGGjE5U/yxHTMaCiYycIJkiougJ0G9mPDpmJC7hHshHKX8WvYs+fOb7LQ== 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=jbrYLpHnX3WNUjZlnzkkhqrZbNvy24fvuDRqDOUnEw4=; b=fPTrbjPfd8pkNNW50uBiDOxnZWiHxYm+JHYUtzfpX5lBPG7uZyzSMSrfF1GnBlv3HwFSKRdooQvQ8QJHfquFtkbsYoQfDdW/UhTY0y9pvC0PmrDYGA+AXDl1/TVGkOGKxoLIPw/fPPnaRdHAQQ1Fda+G80s188sRfG+zzUg+n/ygPxgYu4/nsttTJcrb3xkG8N/oZ6P0HbWFOgwmCoYhecUsmlor3maybDrRaqgXACTq74Zdx0vAgWByuzrmiz9PPBBi17Rz4hZkAnlaURHovoX7kr0ZykNzR+UzzEb3emGgqVRtX2dxfoTRGsXA0dQ878km0koYngFhdUZqa29Ktw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=jbrYLpHnX3WNUjZlnzkkhqrZbNvy24fvuDRqDOUnEw4=; b=vB39RkcxOVuBsV5fcvPGGemvnTDpxNNV4aDXjYf65t+p1+oqNGml3mSK8mwIPnj6jzvSZtZlWKlBaPIZ3MYaFyohhYeLjl+Zd/MhWFValZ/nOb+8TINtQtdvtB7qzDE/G9SsAzmQoq8zxD44heFPkSo+YPsv5tELplpziLHLWaQ= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from DS7PR12MB6048.namprd12.prod.outlook.com (2603:10b6:8:9f::5) by DS4PR12MB9564.namprd12.prod.outlook.com (2603:10b6:8:27e::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8922.36; Wed, 16 Jul 2025 09:46:42 +0000 Received: from DS7PR12MB6048.namprd12.prod.outlook.com ([fe80::6318:26e5:357a:74a5]) by DS7PR12MB6048.namprd12.prod.outlook.com ([fe80::6318:26e5:357a:74a5%5]) with mapi id 15.20.8922.035; Wed, 16 Jul 2025 09:46:42 +0000 Message-ID: <529c8436-1aeb-41bc-94bd-8b0f128e6222@amd.com> Date: Wed, 16 Jul 2025 15:16:27 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 4/4] iommu/amd: Fix host kdump support for SNP To: Ashish Kalra , joro@8bytes.org, suravee.suthikulpanit@amd.com, thomas.lendacky@amd.com, Sairaj.ArunKodilkar@amd.com, herbert@gondor.apana.org.au Cc: seanjc@google.com, pbonzini@redhat.com, will@kernel.org, robin.murphy@arm.com, john.allen@amd.com, davem@davemloft.net, bp@alien8.de, michael.roth@amd.com, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, kvm@vger.kernel.org References: Content-Language: en-US From: Vasant Hegde In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: PN4P287CA0107.INDP287.PROD.OUTLOOK.COM (2603:1096:c01:276::10) To DS7PR12MB6048.namprd12.prod.outlook.com (2603:10b6:8:9f::5) Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB6048:EE_|DS4PR12MB9564:EE_ X-MS-Office365-Filtering-Correlation-Id: 4c3faf0d-054b-4cd8-a75d-08ddc44dab50 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|7416014; X-Microsoft-Antispam-Message-Info: =?utf-8?B?cFZoY0Z2TDJkYmYyV2I1WXFRSFExSDMyaUZTdG50dy9JVHJGNVdiUFJGeU9C?= =?utf-8?B?NlJieWY4M1ZoNkJtT1VsMjBrTmtndXF6cEs5eXFMRmZmVHZHTzNCQVU0OUgr?= =?utf-8?B?K2xVMHRpaytMakFFd05qOFVRUjluRC9qaFVTVjNTTGFsNjZaT1pUM2pVRGEz?= =?utf-8?B?QVoxNllrSW0vZldlRTRqWW5wNlBENnBGKzNVUEhtR3JBeC9tVU1uZTQ3aTFF?= =?utf-8?B?SWZSRXp5RThuejhPMGdpZUJ1VW4xdC9jdXhaU21IME5HN2QrNmRtN09QYnln?= =?utf-8?B?VndSOFVtN3hkYjRCS2FrQjVSTTNrZHA5RjhmV3RzeEdDUXRlRWhtZThjZkl6?= =?utf-8?B?NUJ0b1BISTd1ZTNJbWVOTkNQUTIzRFA4bWJYc21oOSt1SDFjRXNxRExFN0hC?= =?utf-8?B?cTNyZE12WWErWUpMYjkxalh3UWtQU0dXaGU4aXh4SFlqTG5RL01tYlpDVkZG?= =?utf-8?B?QmFnUGZvOGRIOXJRWTc5VUJGTkdyMktpUS84RUdOMmcvRHQxOUtJVi9PL3JF?= =?utf-8?B?eWYydjZDT0taZ1JPNUdER3diMGh4a3RnOG5LMkVHRXA1Qll3RFpnZGhSNktB?= =?utf-8?B?Vk83eHlnRXkxNEk1bzR4alEyZklqUkRvS29QczdzbkdGNEhSSFZSSnltZzVk?= =?utf-8?B?UU15TUxHSEhXRExTamd2ZnhtbmRwN3h3K1RvNWFRREFOR0ZzeS8xZWMvYlYx?= =?utf-8?B?WlZ0MmhaVjdjY1NJY2xETkZLd0V0a1NBVmc4SjVVeU9MTFM0b0Z5cDlTSmJr?= =?utf-8?B?SGc4OVhZNXVFNnFiV0RWUHhwbSttZ3BvZEIvSlJQYzI0VTJESzd5aXBIcE5F?= =?utf-8?B?c0RmaFhVN3BvTVFqL1F2L2RqUVlzcmR0Rnh1Z2lETGpCajVxTEpNV2ZZa2M3?= =?utf-8?B?dVFVTUp1bEtlWDdrSzRQQkh6TDVXbUt5RXlSNWpxNVNXd2owRHA2Y2dTdkJY?= =?utf-8?B?YWxXdG84aDBFRk5HRXRxOWllTVpHd0xsckxmelB6Y1Jxd2ZGSmpReUhZNWRa?= =?utf-8?B?cHpnN005UXNCYUE3QmdWV2U4WDd6di8wVmg2bHZscGtSSWIyRUZiMXQ5UXNG?= =?utf-8?B?M05ZRTkraHJXd2pSWTl1VXpGTWw2ZVNaZERvRkxDdHdwMUJVT3ZLallPUUg2?= =?utf-8?B?eVF1UGxOdllIWjhlV3NDY1cvMjZSbERiY2dJbzdnUm9ucVlhRjEzRDMvWmxP?= =?utf-8?B?dTlzKzhZMlVYMnVkR3VFTkpWRHE5WWh5d3FnNHd6SngwajJtaVdQWmZKVE0y?= =?utf-8?B?MVVZK2loU09GODZGQ1Z0emgwdU44bTRUNE5CalpjZmtmblQvTlQ2YkpyU3FC?= =?utf-8?B?bFNPZ25nUVV0YTJmNGh1OG0vVjFMS2tIRGlGK0FiSEtYNXhDS0JGMnNMc2tv?= =?utf-8?B?LzFYbjllaFVGY2Z6ZGVaZUIyKzdBaTRzV1ozdGEwVllrSUJKWGhDV2VDVzV3?= =?utf-8?B?VmZHMjRUVEpYMTYxdy9QQnVCOTRUa09raFZkZmphZEZCQmlEWTJBcTFoaUJy?= =?utf-8?B?TkV6T0gxL0JTUWZPWnlnc1B1cVRmMW14ZzZpM1NKeThHbVZvQVVGQ3RZaTJj?= =?utf-8?B?aURhMGxtaUZsck9SdUhZeU00bDZTSy9PTHI5OE5tMkIwMlpFa0xsTCtkeFE4?= =?utf-8?B?V2p2ZnpQblhwODVmd0F3UEYyVDY5WkdFZEVXL1ZIV25wc0RVRy8zTTcyQ1pR?= =?utf-8?B?MGJLUWxXL3FvZ0t5bGNFZFpJcm1jOW1JQWFYUG1EOWs2dXVXMDErRkJ0Qnhx?= =?utf-8?B?eXR2bHU1WFI5enFNZE9jUXdjUjR0Q1dUbnlXdzAvSCtScnkvMlU3b091Z0dO?= =?utf-8?B?bEZZNjJmamNVeDlSVnFaSjNIc2kxbTZ1WkxYUkN5dm4zeEtQcWNpQjI1QzRO?= =?utf-8?B?WFF5K0pYQWFzSFkwa1VrRDdzMncxQ08xTEo1N1dEREY0LzhGZjBZcW9UcWFS?= =?utf-8?Q?LJ97zZtNcSw=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DS7PR12MB6048.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(7416014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?bVZTaVlhWXNGdEtxaVpVVDJFWDVRUks5MitIVVgyQU94NnlKUXZCY0ZBOUNk?= =?utf-8?B?KzlmRjZyeERpdkh3U0JJWVJibTVyK1oxQTRkdTNVZXZXNVVkc2o0M3RXeWwy?= =?utf-8?B?VnEvcEROSWNVTS9RMzJNREo0OUpCNTJndWR1bFdCcW10RVBVN0x3UEM0ZTBy?= =?utf-8?B?RDg1UWxBaHh1ZGJpM1VGVFdrT2orSCtEY0hxcEltTXp2QWc2azFGTUMwYVdM?= =?utf-8?B?blRHaEJZcGJXWlZ4bHUxU0pHeUJsbUd5aGI5c1hsMEppT2hKZ2ZJSTZ6bmpj?= =?utf-8?B?SHk0ZjU2bk9LSXdkQjBXWm5GcXNJeSt4ZjlnZm9Qd3R6ZmNROWJ6ZkRBRkMr?= =?utf-8?B?a0RRbjhwVDdYbldqYjBwOVl1MHBZU2ltMDVOZ3N6K0FROEtxVUx1bmNPY2Rj?= =?utf-8?B?bTduTWo0UDRiMG5mbmVPVWxMNWtLZVFqdU8xdlRiL0VuU29PV25zY3FDTzli?= =?utf-8?B?dG5xNHdDSmwrWjVTMjVLMEFjWEhJVXRFRHVKZjZPei9XYU93eFhGZzhGcHZK?= =?utf-8?B?VG5iLzBSMms0SCt1YjR1T0x5V1pqbkl3bTlSNlF4VVMrd1RaalZ3alpHME8x?= =?utf-8?B?UTQyRGFZUFlRbHN1OEIwVlY5dVU3RXpwQTB5VnZOUDhxVzZmWmFVbVZXb0Ur?= =?utf-8?B?cTdEeUI5N091NTAzV1hiNXRDUCtPdHN6eXYvZjdvYWNWVEowQTBRdksxTHhQ?= =?utf-8?B?TksvNGlQb0E5RUF1TzFoNXk5bGZzdXRxU0FYYW5iUzlnN2FPcmx5Ulp4VVZZ?= =?utf-8?B?TjhIREQzOUdZNXRvMDEwcU5lTEVLSUlOcVRhV3RabGJqVmtDdGdwZUR5NThv?= =?utf-8?B?MmZJRUNHSlVFbGpPV1pEOE1FZXRyRVdjVG5HZlhBMXhpdE5POEhHZTBJTjJy?= =?utf-8?B?eWRVZ00rNmY4TzVrdW96YVRKLzAzdE9vUk44bUw3ai8xU3ZBeTJBbHE1UkQy?= =?utf-8?B?NDRvb29HVTNLaDQwK3FyM0NzcU42NktvdjRKdkJINHl5Z05PbHZoaUdFSks3?= =?utf-8?B?ODNsVEZzc0t0R3Rta1VTK1NoclVGRnBjQ1ZYcjNQdWdwQ1JPaEV0M3d1bk1v?= =?utf-8?B?bUdrMysxZnZGWThQbXhaaWRHRWFwVDBRdnRscTYwaTJYZ3BTQjJZSlVUaDZX?= =?utf-8?B?WVNUNmJHNW5kQ2FPcmZxbkJ2NFY1Y1JrQ2Z0NmdGQm1pN0JLTVhkRzlVUjRz?= =?utf-8?B?c3VYNE5hSnFOTktWTC85WkZnOVVISEpKQUxBYloybnN2ZTRMcTlwdjBBQTAv?= =?utf-8?B?MWg3TTlsdjBaU0IyQXVteFNsRkVrSEF0UjhGV2FvU3F1VDRqZXZrQWc3SS8y?= =?utf-8?B?SzVpWHBwSzdkdU9mR1Q0MEdveWhVQmgzbWpnL0tRS3V0b0lTVUZYampsN2ZZ?= =?utf-8?B?TkN4aDNYSlRhK3FqWGUwZ2dmMTA0akdRVWxxZFMzdDdqN1hMUmZ3bU0wK0sv?= =?utf-8?B?cytCT3RCTGhwWVcrVlduNThuZjFaM2FhanZsMVBIRzFaYmN1LzB0SVFlbFdH?= =?utf-8?B?d1hUNlpHYXAwYmxHd3dsYlhSZDFHTndUOGVpVmkrdlRWaVdvWkh6Uks4b0RE?= =?utf-8?B?ck8wd3VLUG5UeWQ4NVV4Q2VzKzJMaHF2SWFMYlREQkhjMlNmYlpQTjhCZ1ho?= =?utf-8?B?UHU5OUxGK2FJaU1ObG44WmVVd2g1UTUrekc5T3BvdEEzL0FLYnpyRnNYcVpx?= =?utf-8?B?NldpRjNJS1p5U3dvMGlyMVJqUTlFNVViOERmVmpGTzVCa3N0VmdObTRqOEcz?= =?utf-8?B?Y1Q3Yml6Tmx2OU92Z3NueGRKMjBCeGdrcTZ5SE1paU9aNzJURW4zQmJINXlI?= =?utf-8?B?VHJSK2ZFVFYxdnk1Znc2SDBVcVJnZjd4b2dHek8xV09zMmpObGNnNkpHODlj?= =?utf-8?B?MWVEVXR6TVdYKzdxMFFoa3pPTG9oOStGU1BYbzlPVVVCRzFFajFFdHhkUG15?= =?utf-8?B?QmJzaDNEa0NuMFNEdlJmb3NNZWc5VFJjdTdoZ1dGNlBrdGxyWWJRaEJVK0xy?= =?utf-8?B?aklHUmFqY2lMdEY4eXBCaGpIU0VZMUZteEtrNEZ6Y0pUdTNkSDFNSEx2aEdu?= =?utf-8?B?SCtvWFltSm5sekFiaXl3RDcwYXVvb21LaWUxc0FiUlJKR2oydnFON0dyamFx?= =?utf-8?Q?iggt+kCPr+DDicSevYi866yFo?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4c3faf0d-054b-4cd8-a75d-08ddc44dab50 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB6048.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jul 2025 09:46:42.5919 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: uzaXDTQ6rfnQTz54vbozly6BVcfmTpk4d9UhOUdI1RCntZ4+4LfRIqpCX0/bLpz6oi58rq0mD8567oGkCUqqlw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS4PR12MB9564 On 7/16/2025 12:57 AM, Ashish Kalra wrote: > From: Ashish Kalra > > When a crash is triggered the kernel attempts to shut down SEV-SNP > using the SNP_SHUTDOWN_EX command. If active SNP VMs are present, > SNP_SHUTDOWN_EX fails as firmware checks all encryption-capable ASIDs > to ensure none are in use and that a DF_FLUSH is not required. If a > DF_FLUSH is required, the firmware returns DFFLUSH_REQUIRED, causing > SNP_SHUTDOWN_EX to fail. > > This casues the kdump kernel to boot with IOMMU SNP enforcement still > enabled and IOMMU completion wait buffers (CWBs), command buffers, > device tables and event buffer registers remain locked and exclusive > to the previous kernel. Attempts to allocate and use new buffers in > the kdump kernel fail, as the hardware ignores writes to the locked > MMIO registers (per AMD IOMMU spec Section 2.12.2.1). > > As a result, the kdump kernel cannot initialize the IOMMU or enable IRQ > remapping which is required for proper operation. > > This results in repeated "Completion-Wait loop timed out" errors and a > second kernel panic: "Kernel panic - not syncing: timer doesn't work > through Interrupt-remapped IO-APIC" > > The following MMIO registers are locked and ignore writes after failed > SNP shutdown: > Device Table Base Address Register > Command Buffer Base Address Register > Event Buffer Base Address Register > Completion Store Base Register/Exclusion Base Register > Completion Store Limit Register/Exclusion Range Limit Register > May be you can rephrase the description as first patch covered some of these details. > Instead of allocating new buffers, re-use the previous kernel’s pages > for completion wait buffers, command buffers, event buffers and device > tables and operate with the already enabled SNP configuration and > existing data structures. > > This approach is now used for kdump boot regardless of whether SNP is > enabled during kdump. > > The fix enables successful crashkernel/kdump operation on SNP hosts > even when SNP_SHUTDOWN_EX fails. > > Fixes: c3b86e61b756 ("x86/cpufeatures: Enable/unmask SEV-SNP CPU feature") I am not sure why you have marked only this patch as Fixes? Also it won't fix the kdump if someone just backports only this patch right? -Vasant