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Wysocki" , Max Gurtovoy , Bjorn Helgaas , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-pm@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH v3 8/8] vfio/pci: Add the support for PCI D3cold state Message-ID: <20220601231720.GT1343366@nvidia.com> References: <68463d9b-98ee-b9ec-1a3e-1375e50a2ad2@nvidia.com> <42518bd5-da8b-554f-2612-80278b527bf5@nvidia.com> <20220530122546.GZ1343366@nvidia.com> <20220531194304.GN1343366@nvidia.com> <20220531165209.1c18854f.alex.williamson@redhat.com> <00b6e380-ecf4-1eaf-f950-2c418bdb6cac@nvidia.com> <20220601102151.75445f6a.alex.williamson@redhat.com> <20220601173054.GS1343366@nvidia.com> <20220601121547.03ebbf64.alex.williamson@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220601121547.03ebbf64.alex.williamson@redhat.com> X-ClientProxiedBy: BL0PR02CA0124.namprd02.prod.outlook.com (2603:10b6:208:35::29) To MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: d57344bf-511b-403c-0bba-08da4424e116 X-MS-TrafficTypeDiagnostic: BN8PR12MB2961:EE_ X-Microsoft-Antispam-PRVS: 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?GLkTqOdsaZt85s7EIPafH/pr4kvqL5CQ9Gko/a1cMzj/n8miiePsfwEjucbv?= =?us-ascii?Q?E5rgRHzHFwfJi3R16g8Fs9ZVM60EN4OfTYAXxsvsd8wOLFPVVJ8taFdYKr19?= =?us-ascii?Q?N7AFZWH0ag7Jf6FbBGHvZZ5k2iH0PD9mqKRJUtp2vEYnKmhpB5I1LIwglqSM?= =?us-ascii?Q?Hhh2pkoct/vtmR9hsNgKyh9ooCtkDSuyYuzDK7875L1HBRaZyylxcRU56dPV?= =?us-ascii?Q?Nv3PsZ7sq6hGoDtkt9ioONn0gEjB0xpXRBRhoDNf4UrY/s99RDjqDwGZUaCc?= =?us-ascii?Q?bBwP4yHVbwVAvU9JsTpWeglXsybdKJcIOOYz5OzG6xQ79cmvVfB0OUc505aO?= =?us-ascii?Q?EOKI5fTUFjVgco7crlulk0oXNR+RwYE1izm2aA+1sR69599/WH1qofdSoPjz?= =?us-ascii?Q?NGikVw+yb18PXiDojaIpQ3BgfjddQpP7ZOiBB+qEt6/TLVxdisWSfuDlBDMQ?= =?us-ascii?Q?MQVmXle2AKlAnlB2m9+y6hk3yyRRJQus7PuR1X94l7EUetEr4xMggOLHk2Qs?= =?us-ascii?Q?7I5l7Qx1QjWAemMqG4zKGbZO4pXEWBViDnzGJ7wSBVZN9wEF3GYQ8LE4C7to?= =?us-ascii?Q?d5u+X1JRKnzS+OLr5V2dP/f6rcsNsIcvpf9gcFNEtM1QI1+jgIGPnMEfcMpL?= =?us-ascii?Q?jV0Kpr6M57txb7vMY8bnDiEGmKtgUF/qJx8Sj3KNPooT+9lb8QRsg/r9C1Oh?= =?us-ascii?Q?iPGXioshh5QORbwyMN1rCGvyrKt1J/HuPfVfHyEixKayrLMuQejey4NGIMZa?= =?us-ascii?Q?U6+IaxiELBZMW3ORJSkxeLOFyLrOMqYqmMFcA7zJdQv61i3lSGY9DBNDL4iB?= =?us-ascii?Q?7y4kacUvcL7nwbi1xkF2IzCVuLA52HK0M94iOO4ONNZTtgEeD4ZBiDzxOTS/?= =?us-ascii?Q?o6jGTAoaHhYIwSleomZHVCh2saHsTSgCef19uMofyEYKLXYDZzXNZqDXjHYG?= =?us-ascii?Q?5ZhBZxvi4BlnkUODcm7ZGyGMLWmPmmL4pLaoCZLadq1fl4rvOIomSVh/IVrJ?= =?us-ascii?Q?YCVVBDyccH9EJy48VUbXErlDqg2LAY4lOl3x2YhE4aOQOpXE4gWjCS9eiu7a?= =?us-ascii?Q?EYcpo9QqU1ETNcJJkA2Mp8QPOleXK6AUkCm+R0COkzcWNdnjmgXKOBCkHHQY?= =?us-ascii?Q?kaw35Htp4Im9HyTljqlxUSXz53t3vKJJGQ5VyPJNgM6xq3Yzys66AOKUnTeB?= =?us-ascii?Q?O5XeAub8R0oDLnq/cGd5yLG4X+aNrqUYXtWTZHEdjkCDErEvjJoLiQsLbXV9?= =?us-ascii?Q?BnmU0h+jLirT83Sj9zUNud8Ihqi682+xkrIzWY/aroEGma5Sz2kcvFJm+SWy?= =?us-ascii?Q?KlhwOWCFCDljNgdmVCF0WIZw2n+kph7graRFd0hInRNIsR+ereudXEVu+GRn?= =?us-ascii?Q?7oM9gVj3VpjBuBy0w5pWk3ylzGI7JWXG6wW5lQxosLY1c1BfADGJ6z3YbbL+?= =?us-ascii?Q?IxsK0Obp5LNJmaT9sD6T9mD1fRULg2DS/8v81Oek4NfcblMP8iYt3Hvhv4XP?= =?us-ascii?Q?JBdp02x83enKyXOlwmmGiNEP+ciU160hRS4nNcDKVCltPMcOWfcZQ6Gbr7MX?= =?us-ascii?Q?HeIMaRcrMRPaLnZoqLBTOUPNKJ23smfX4F4Kt2+io6Uamv/p3FvIPv2847dK?= =?us-ascii?Q?kEqXfy39/gCF5w6eR2EqlmOoCMRRoUCEib8lr5IewdfnOIkayeAIjgcAkO86?= =?us-ascii?Q?uuz3rwrkLybMFCOhbR6wT0EQexY3Z7r71T+HNUw/3f1KYjqDDFGZuGzo5i3U?= =?us-ascii?Q?7em6LuxSJg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: d57344bf-511b-403c-0bba-08da4424e116 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Jun 2022 23:17:21.4219 (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: Z3dXal2lwGJUs9dySq0xlsm/+Ny8LVu4l5MMiewlL5rHvYljLF3PtQz584ZbVpD2 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR12MB2961 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 01, 2022 at 12:15:47PM -0600, Alex Williamson wrote: > On Wed, 1 Jun 2022 14:30:54 -0300 > Jason Gunthorpe wrote: > > > On Wed, Jun 01, 2022 at 10:21:51AM -0600, Alex Williamson wrote: > > > > > Some ioctls clearly cannot occur while the device is in low power, such > > > as resets and interrupt control, but even less obvious things like > > > getting region info require device access. Migration also provides a > > > channel to device access. > > > > I wonder what power management means in a case like that. > > > > For the migration drivers they all rely on a PF driver that is not > > VFIO, so it should be impossible for power management to cause the PF > > to stop working. > > > > I would expect any sane design of power management for a VF to not > > cause any harm to the migration driver.. > > Is there even a significant benefit or use case for power management > for VFs? The existing D3hot support should be ok, but I imagine to > support D3cold, all the VFs and the PF would need to move to low power. > It might be safe to simply exclude VFs from providing this feature for > now. I know of no use case, I think it would be a good idea to exclude VFs. > Yes, but that's also penalizing devices that require no special > support, for the few that do. I'm not opposed to some sort of > vfio-pci-nvidia-gpu variant driver to provide that device specific > support, but I'd think the device table for such a driver might just be > added to the exclusion list for power management support in vfio-pci. > vfio-pci-core would need some way for drivers to opt-out/in for power > management. If you think it can be done generically with a small exclusion list then that probably makes sense. Jason