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Thu, 11 Mar 2021 17:01:46 +0000 Received: from DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::1c62:7fa3:617b:ab87]) by DM6PR12MB3834.namprd12.prod.outlook.com ([fe80::1c62:7fa3:617b:ab87%6]) with mapi id 15.20.3933.031; Thu, 11 Mar 2021 17:01:46 +0000 Date: Thu, 11 Mar 2021 13:01:44 -0400 From: Jason Gunthorpe To: Alexey Kardashevskiy Cc: Max Gurtovoy , alex.williamson@redhat.com, cohuck@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, liranl@nvidia.com, oren@nvidia.com, tzahio@nvidia.com, leonro@nvidia.com, yarong@nvidia.com, aviadye@nvidia.com, shahafs@nvidia.com, artemp@nvidia.com, kwankhede@nvidia.com, ACurrid@nvidia.com, cjia@nvidia.com, yishaih@nvidia.com, mjrosato@linux.ibm.com, hch@lst.de Subject: Re: [PATCH 8/9] vfio/pci: export nvlink2 support into vendor vfio_pci drivers Message-ID: <20210311170144.GM2356281@nvidia.com> References: <19e73e58-c7a9-03ce-65a7-50f37d52ca15@ozlabs.ru> <8941cf42-0c40-776e-6c02-9227146d3d66@nvidia.com> <20210310130246.GW2356281@nvidia.com> <3b772357-7448-5fa7-9ecc-c13c08df95c3@ozlabs.ru> <20210310194002.GD2356281@nvidia.com> <7f0310db-a8e3-4045-c83a-11111767a22f@ozlabs.ru> <20210311013443.GH2356281@nvidia.com> <20210311020056.GI2356281@nvidia.com> <73c99da0-6624-7aa2-2857-ef68092c0d07@ozlabs.ru> Content-Type: text/plain; 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For example, the Intel IGD driver > and vfio-pci-igd - how should the system pick one? If there is no > MODULE_DEVICE_TABLE in vfio-pci-xxx, is the user supposed to try binding all > vfio-pci-xxx drivers until some binds? We must expose some MODULE_DEVICE_TABLE like thing to userspace. Compiling everything into one driver and using if statements was only managable with these tiny drivers - the stuff that is coming are big things that are infeasible to link directly to vfio_pci.ko I'm feeling some general consensus around this approach (vs trying to make a subdriver) so we will start looking at exactly what form that could take soon. The general idea would be to have a selection of extended VFIO drivers for PCI devices that can be loaded as an alternative to vfio-pci and they provide additional uapi and behaviors that only work on specific hardware. nvlink is a good example because it does provide new API and additional HW specific behavior. A way for userspace to learn about the drivers automatically and sort out how to load and bind them. I was thinking about your earlier question about FDT - do you think we could switch this to a platform_device and provide an of_match_table that would select correctly? Did IBM enforce a useful compatible string in the DT for these things? Jason