On Fri, Nov 08, 2019 at 05:05:45PM -0400, Jason Gunthorpe wrote: > On Fri, Nov 08, 2019 at 01:34:35PM -0700, Alex Williamson wrote: > > On Fri, 8 Nov 2019 16:12:53 -0400 > > Jason Gunthorpe <jgg@xxxxxxxx> wrote: > > > > > On Fri, Nov 08, 2019 at 11:12:38AM -0800, Jakub Kicinski wrote: > > > > On Fri, 8 Nov 2019 15:40:22 +0000, Parav Pandit wrote: > > > > > > The new intel driver has been having a very similar discussion about how to > > > > > > model their 'multi function device' ie to bind RDMA and other drivers to a > > > > > > shared PCI function, and I think that discussion settled on adding a new bus? > > > > > > > > > > > > Really these things are all very similar, it would be nice to have a clear > > > > > > methodology on how to use the device core if a single PCI device is split by > > > > > > software into multiple different functional units and attached to different > > > > > > driver instances. > > > > > > > > > > > > Currently there is alot of hacking in this area.. And a consistent scheme > > > > > > might resolve the ugliness with the dma_ops wrappers. > > > > > > > > > > > > We already have the 'mfd' stuff to support splitting platform devices, maybe > > > > > > we need to create a 'pci-mfd' to support splitting PCI devices? > > > > > > > > > > > > I'm not really clear how mfd and mdev relate, I always thought mdev was > > > > > > strongly linked to vfio. > > > > > > > > > > > > > > > > Mdev at beginning was strongly linked to vfio, but as I mentioned > > > > > above it is addressing more use case. > > > > > > > > > > I observed that discussion, but was not sure of extending mdev further. > > > > > > > > > > One way to do for Intel drivers to do is after series [9]. > > > > > Where PCI driver says, MDEV_CLASS_ID_I40_FOO > > > > > RDMA driver mdev_register_driver(), matches on it and does the probe(). > > > > > > > > Yup, FWIW to me the benefit of reusing mdevs for the Intel case vs > > > > muddying the purpose of mdevs is not a clear trade off. > > > > > > IMHO, mdev has amdev_parent_ops structure clearly intended to link it > > > to vfio, so using a mdev for something not related to vfio seems like > > > a poor choice. > > > > Unless there's some opposition, I'm intended to queue this for v5.5: > > > > https://www.spinics.net/lists/kvm/msg199613.html > > > > mdev has started out as tied to vfio, but at it's core, it's just a > > device life cycle infrastructure with callbacks between bus drivers > > and vendor devices. If virtio is on the wrong path with the above > > series, please speak up. Thanks, > > Well, I think Greg just objected pretty strongly. Yes I did. I keep saying this again and again, and so did you here: > IMHO it is wrong to turn mdev into some API multiplexor. That is what > the driver core already does and AFAIK your bus type is supposed to > represent your API contract to your drivers. That is exactly right. Don't re-create the driver api interface at another layer please. thanks, greg k-h
