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Thu, 24 Aug 2023 17:19:12 +0000 Received: from SJ2PR11MB7573.namprd11.prod.outlook.com ([fe80::47e:3e1f:bef4:20e0]) by SJ2PR11MB7573.namprd11.prod.outlook.com ([fe80::47e:3e1f:bef4:20e0%3]) with mapi id 15.20.6699.027; Thu, 24 Aug 2023 17:19:06 +0000 Message-ID: <84629316-dafa-9f4e-89e9-40ccaee016de@intel.com> Date: Thu, 24 Aug 2023 10:19:02 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.14.0 Subject: Re: [RFC PATCH 2/3] vfio/ims: Support emulated interrupts Content-Language: en-US To: Jason Gunthorpe CC: , , , , , , , , , , References: <7a08c41e1825095814f8c35854d3938c084b2368.1692892275.git.reinette.chatre@intel.com> From: Reinette Chatre In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MW4PR03CA0309.namprd03.prod.outlook.com (2603:10b6:303:dd::14) To SJ2PR11MB7573.namprd11.prod.outlook.com (2603:10b6:a03:4d2::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ2PR11MB7573:EE_|DM4PR11MB5455:EE_ X-MS-Office365-Filtering-Correlation-Id: 6872073e-7177-474c-ddc5-08dba4c63828 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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For example, a virtual device may use 'intercepted >> path' for configuration. Doing so, configuration requests intercepted >> by the virtual device driver are handled within the virtual device >> driver with completion signaled to the guest without interacting with >> the underlying hardware. > > Why does this have anything to do with IMS? I thought the point here > was that IMS was some back end to the MSI-X emulation - should a > purely emulated interrupt logically be part of the MSI code, not IMS? You are correct, an emulated interrupt is not unique to IMS. The target usage of this library is by pure(?) VFIO devices (struct vfio_device). These are virtual devices that are composed by separate VFIO drivers. For example, a single resource of an accelerator device can be composed into a stand-alone virtual device for use by a guest. Through its API and implementation the current VFIO MSI code expects to work with actual PCI devices (struct vfio_pci_core_device). With the target usage not being an actual PCI device the VFIO MSI code was not found to be a good fit and thus this implementation does not build on current MSI support. Reinette