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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Apr 12, 2023 at 01:43:26PM +0100, Marc Zyngier wrote: > What makes it safe? How does VFIO ensures that the memory type used is > correct in all circumstances? This has to hold for *ANY* device, not > just your favourite toy of the day. Nothing in this patch is horribly > wrong, but the above question must be answered before we can consider > any of this. In VFIO we now have the concept of "variant drivers" which work with specific PCI IDs. The variant drivers can inject device specific knowledge into VFIO. In this series the driver injects the cachable pgprot when it creates some of the VMAs because it knows the PCI IDs it supports, parses the ACPI description, and knows for sure that the memory it puts in the cachable VMA is linked with a cache coherent interconnect. The generic vfio-pci path is not changed, so 'any device' is not relevant here. 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Wed, 12 Apr 2023 13:01:36 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::6045:ad97:10b7:62a2]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::6045:ad97:10b7:62a2%9]) with mapi id 15.20.6277.038; Wed, 12 Apr 2023 13:01:36 +0000 Date: Wed, 12 Apr 2023 10:01:33 -0300 From: Jason Gunthorpe To: Marc Zyngier Cc: ankita@nvidia.com, alex.williamson@redhat.com, naoya.horiguchi@nec.com, oliver.upton@linux.dev, aniketa@nvidia.com, cjia@nvidia.com, kwankhede@nvidia.com, targupta@nvidia.com, vsethi@nvidia.com, acurrid@nvidia.com, apopple@nvidia.com, jhubbard@nvidia.com, danw@nvidia.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v3 1/6] kvm: determine memory type from VMA Message-ID: References: <20230405180134.16932-1-ankita@nvidia.com> <20230405180134.16932-2-ankita@nvidia.com> <86r0spl18x.wl-maz@kernel.org> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <86r0spl18x.wl-maz@kernel.org> X-ClientProxiedBy: SJ0PR03CA0387.namprd03.prod.outlook.com (2603:10b6:a03:3a1::32) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|IA0PR12MB8906:EE_ X-MS-Office365-Filtering-Correlation-Id: 890c33a8-c11b-46d7-2a95-08db3b560c40 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?kyBSMxjfGEXSPEPMNnOvL1tko02uEcnpL8wxccB0M4ZuLdJtAZJuvTrJdPp6?= =?us-ascii?Q?d79l6SMhtsIhMsgqCpr8MI2K/QMesda1dcOpn85254gl8hK5x4Dh5MTRB6Sh?= =?us-ascii?Q?mjArov4XjM6PXqVUUe9Jd/WSszv8G9b22Rrmjm7yhj39yehxlGzNsu/ReiBD?= =?us-ascii?Q?ac2vd04/fM3NutfW2o1tNHIalRIOV7cjIK0c30goS2Pdf1D1R3VPoLWu9GP6?= =?us-ascii?Q?/A03A93Hnd+YQctYfd6H3dRq1hRVrzC511Qsa6Sf6ExCAu+rs7NEMx0IwoMn?= =?us-ascii?Q?m2c7v8lqtSLrkOb+xZGx7ltWDlF03kMMesHnjP/phQ1f2e8b43zeSFahIu6M?= =?us-ascii?Q?wkSROUYZjH+GHyOrTNwyOO+Cnwxfeg1HPCz85DALKtZo/ARM+RmOvou4nVAk?= =?us-ascii?Q?d9s2m1/nm0Kc/YTuGPuEbGF2RlLgH5ZopzknWz1dKlkPx3wPDMHWWeslwtVF?= =?us-ascii?Q?ahfK4I2OMCd1XkowW+QF5nPbVIQQCv+MD6CZ3cWnjPf0FqzP4DQX0Y2Y3Hdi?= =?us-ascii?Q?41muX1pMseZ9irdtsEjDZMPjzeNrNBeBGqNJ6Lh32RdvmuImHo5xOP+uxz0E?= =?us-ascii?Q?5vqJL2vIcbRxoFicNU390n3Ph3/Lrm5l15cmw6PB8pC0rSTBS1kSJ7OiIflW?= =?us-ascii?Q?2sRyon0TSqU/c/gSbMwvV0J5+bB7HIeiOKyAZSlbJKB77kfyQMU3fwsytgR2?= =?us-ascii?Q?BWp6fIxDwlwYh6qBvq1Wl4godPebj/ykeX4799ZVRQON3mEeXNYZh3qyqKcr?= =?us-ascii?Q?Yo7xiNhzJornCwNPtRP93TWpC6wz0SHNBJxwfmuIMPIpkg1rqgUEyp/Q1ZGO?= =?us-ascii?Q?33KytGtEvRrq2hApAqEQI7VdCAeT+2vmF4F0dCeIq4ahRuMDiHe9zkPtbdAm?= =?us-ascii?Q?74RCQ1ayE6giMxipRxYe9e0o5uvcS7jXFFHFo3Pc4cyQpdX/OWbzs3aSn2CT?= =?us-ascii?Q?o953Y3kviZ6zhMHPQGRSviT2F0qm8rbbU0pBWJ9W6MBO4XzxvnOlAHgE5MQH?= =?us-ascii?Q?nn/WFU72Rjh/TSon7mUfOWGnEN4xE7bQwFpYnT8G74yxPTKBf/J8KGUWad0j?= =?us-ascii?Q?HMRcDJpGhFpmLia9ZdYsu+dAwvhAUw2lMTxobB/f5K2GEu09B/6L3r7yqwNA?= =?us-ascii?Q?A9+dB0nXJRi54EXqs6FEXEYrNbie3ltxw6L5AjhyVAWnWJ1tlrAmod97GNNg?= =?us-ascii?Q?GKuXWY8qd5IjjKq6Z74ofnwYGvFri/l98A9tjsqea0jNgF1BG23sGnwIbEiS?= =?us-ascii?Q?8YGsszTjzZLexyKnYhwExN3qv9NJ2tEVezvRYV9fe9DBYcopvhrUxaIXZmUo?= =?us-ascii?Q?i06MqehQWRUDu4dBYASIqZe06jZkECz6XGr7GV3K1RmPSRjmnM1NkJfZdcfM?= =?us-ascii?Q?eZ37ZYkZhqag/oxxmLll7Ucd9PuDFILCELrMHKU3ilG1uwoQSGpr+0V61+IZ?= =?us-ascii?Q?ezmKnpVNJgpPgwVPhfzGBYM33rBoz6PJzD9KLwljo+PKXCgcnmZ6RL499kXV?= =?us-ascii?Q?m2N0dlAIxqQECbzVQFlr2ytfhzgPKWo8RaydP5/qhmaDhEZN8YIXhwH/DB8H?= =?us-ascii?Q?jDhth6/+llgoBuf/n4ZQEbIP6FtoT0CObtkGd+Xv?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 890c33a8-c11b-46d7-2a95-08db3b560c40 X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Apr 2023 13:01:36.3795 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: npvKj0LiFF9gj3v6v8W5upWbfCd3fi3EkZPS8Ch2Et0xDvhhcebx+dWAcrED1OeQ X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR12MB8906 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Apr 12, 2023 at 01:43:26PM +0100, Marc Zyngier wrote: > What makes it safe? How does VFIO ensures that the memory type used is > correct in all circumstances? This has to hold for *ANY* device, not > just your favourite toy of the day. Nothing in this patch is horribly > wrong, but the above question must be answered before we can consider > any of this. In VFIO we now have the concept of "variant drivers" which work with specific PCI IDs. The variant drivers can inject device specific knowledge into VFIO. In this series the driver injects the cachable pgprot when it creates some of the VMAs because it knows the PCI IDs it supports, parses the ACPI description, and knows for sure that the memory it puts in the cachable VMA is linked with a cache coherent interconnect. The generic vfio-pci path is not changed, so 'any device' is not relevant here. Jason