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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 v5 1/5] vfio: Add the device features for the low power entry and exit Message-ID: References: <20220719121523.21396-2-abhsahu@nvidia.com> <20220721163445.49d15daf.alex.williamson@redhat.com> <20220725160928.43a17560.alex.williamson@redhat.com> <20220726172356.GH4438@nvidia.com> <20220801124253.11c24d91.alex.williamson@redhat.com> <20220802094128.38fba103.alex.williamson@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220802094128.38fba103.alex.williamson@redhat.com> X-ClientProxiedBy: BL1P223CA0022.NAMP223.PROD.OUTLOOK.COM (2603:10b6:208:2c4::27) 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: ca652ef4-c87d-4267-bf60-08da74a4f46b X-MS-TrafficTypeDiagnostic: DM4PR12MB6496:EE_ 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?BIQcxWrUGrVl+N0b/ceNNGtFk8quMX2x9zVH1yE+wksZhKMSgmdxaPW/o6Ib?= =?us-ascii?Q?WnbMSV611dp85/CDlcTSJfJ9w3BFK1XACJB9aUlG1s6zlvBIdaOXeKeVdFi1?= =?us-ascii?Q?7la+4OyIvGPIyVrSzsLElmf5bcGS9Oimu/+DSUYJahSkJQDywSzIX9skLelC?= =?us-ascii?Q?NYsi1yOQjNrVgePCxbzti0lezjLGOlkZXlw3jIIsn+Mm17tqPrHA4XiyCbU+?= =?us-ascii?Q?Kv6wI1Kbn4RPf8OdS/C0TJ57xce5U3vI/0WxOHx9T6ohLzZ+tqS3ka01/E5Y?= =?us-ascii?Q?+XwqL9cCcSrtQLgg3lDrbs+tLwumPuiPgIcep8uX/Wq1YtF4Q6rDedxC6nDe?= =?us-ascii?Q?3WgmoTnJN29Di0tePabEzp3CcD6g72KIzrIDUAobtIlz+MmAEBf7g4Zzrwqt?= =?us-ascii?Q?CeGdzRveK5CZ9cpvyzC2eLq+9wBi4PliDJJVqcsdhG/lCXw97lSeKuORF6Ch?= =?us-ascii?Q?QqpkkhFSmnJaojuGbaMuCmrr7zopBZz26ZNlD4cqdlhFUA76e51A/aOPqcgm?= =?us-ascii?Q?uOadec970mBmWbfk4sURDt79UoixrNSEci37Z1Zh0PWRsNz5K1OFaM3OovzZ?= =?us-ascii?Q?OThhvtNhqFxsROqOWbY7PzjKnVU7nsTSTEMeY7bSVlG8t7nZq+zXMQdlgQ7L?= =?us-ascii?Q?dPMrhZCA+fz3IjvFsU6qBhZW+yRfg/VmALgLjqGR5HrIy3MyTkkOLXdA2P2u?= =?us-ascii?Q?1zeaizgynZh7mn2tryI7PUFtHwt3HMJZsaReNDg+7kwZucp5Bsdrx8KHtf+k?= =?us-ascii?Q?x6bXdjZqjYcQYVSHsfn2QvzJ34SOqmXY1dBKCmyShTHjsK/WrYRDJbMhpiQE?= =?us-ascii?Q?Jb3pvze6yBzQtIQ4J8UIdgzovbi9efsB9NZrpCWgcadTrGIfZWAJ258dggEq?= =?us-ascii?Q?nI6klSl4rbVsPTpmsvG6goqJFn9HLmTLH8EDu0tG2wIduEroTsMp93Kx/WjK?= =?us-ascii?Q?S7eECcZeqzyjsJXg0zvDEHnXEJbs6A652rp+J4chd9+KTvU19tkOAWVWWdkz?= =?us-ascii?Q?0dmGLX/9fQEmCpVuuLiwuuCq8zNsRnEM32ZQwLO3oh3AD9YQDZX49XQytHZ+?= =?us-ascii?Q?CfXiYXoiCMuDOE3v1t34b6uG+VNrH/Zkj8oxfn1PSkshKoXaZN5/SFNHrziV?= =?us-ascii?Q?HhuxLq7ML2MSTkvJqiLJbgL98Xv//M0rptAJ+Gssq3UqsizvijPIgAE+k+uE?= =?us-ascii?Q?KjFRPNBndaL8O+B1KM/W9RY+YJwqdcn0YdfmRjkEb9wlejygO6fLIkwX6bB+?= =?us-ascii?Q?LzoaEKDUcwbDNoRq7IIPPahy23+phDDy0qbkbPLwWyKg2ME6imb8gE1gMFUd?= =?us-ascii?Q?vD8oEnvUNDqlCqihR0wdY7vkNz8x4LeXEUuqK9K4ROpAoh0uu0e4dhn4jBDH?= =?us-ascii?Q?2m3AqVvya77tCQ77t7y9irdEN8alUo8tHrqOTzKVfCQW+0Y81DFwLbWDRQ2r?= =?us-ascii?Q?AabZeyTYK+0vnJ43CH1rP43GbQaxEEbkgd2Jajne+VhKUB0KqjP52fUdkYsK?= =?us-ascii?Q?cVk5CGCh0yaRzIcjCgIcmLegeb2miNir4xRLVAEe7029YFphvPoZV7ZV6UyE?= =?us-ascii?Q?fCc338D+2c8Ot7EqjKEEMiKcHSqVrV7LjJl4n9ri?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: ca652ef4-c87d-4267-bf60-08da74a4f46b X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Aug 2022 16:35:05.1600 (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: qXvK0Vg8lFwlyPcp3SOkfSEAyOfLghG3JN1rmv+c4KQX7eEnOK9G9b2Ag35Zi1p1 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6496 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Aug 02, 2022 at 09:41:28AM -0600, Alex Williamson wrote: > The subtlety is that there's a flag and a field and the flag can only > be set if the field is set, the flag can only be clear if the field is > clear, so we return -EINVAL for the other cases? Why do we have both a > flag and a field? This isn't like we're adding a feature later and the > flag needs to indicate that the field is present and valid. It's just > not a very clean interface, imo. Thanks, That isn't how I read Abhishek's proposal.. The eventfd should always work and should always behave as described "The notification through the provided eventfd will be generated only when the device has entered and is resumed from a low power state" If userspace provides it without LOW_POWER_REENTERY_DISABLE then it still generates the events. The linkage to LOW_POWER_REENTERY_DISABLE is only that userspace probably needs to use both elements together to generate the auto-reentry behavior. Kernel should not enforce it. Two fields, orthogonal behaviors. Jason