Hi Thomas, > -----Original Message----- > From: Thomas Monjalon <tho...@monjalon.net> > Sent: Friday, June 11, 2021 3:54 PM > To: Yigit, Ferruh <ferruh.yi...@intel.com>; Xia, Chenbo <chenbo....@intel.com> > Cc: Xueming Li <xuemi...@nvidia.com>; Viacheslav Ovsiienko > <viachesl...@nvidia.com>; dev@dpdk.org; pa...@nvidia.com; j...@nvidia.com > Subject: Re: [dpdk-dev] [RFC 00/14] mlx5: support SubFunction > > 11/06/2021 07:14, Xia, Chenbo: > > From: Thomas Monjalon <tho...@monjalon.net> > > > 10/06/2021 12:33, Ferruh Yigit: > > > > On 5/27/2021 2:37 PM, Xueming Li wrote: > > > > > SubFunction [1] is a portion of the PCI device, a SF netdev has its > > > own > > > > > dedicated queues(txq, rxq). A SF shares PCI level resources with other > > > > > SFs and/or with its parent PCI function. Auxiliary bus is the > > > > > fundamental of SF. > > > > > > > > > > This patch set introduces SubFunction support for mlx5 PMD driver > > > > > including class net, regex, vdpa and compress. > > > > > > > > > > > > > There is already an mdev patch, originated from long ago. Aren't > > > subfunctions > > > > presented as mdev device? If so can't we use mdev for it? > > > > > > No unfortunately that's different. > > > mlx5 SF is based on top of auxiliary bus in the kernel/sysfs. > > > > Just out of curiosity: > > > > Does SF use mdev before aux bus is introduced in kernel. I see some history > > of it but am not sure: [1] seems SF was base on mdev. [2] seems BlueField > > software v2.5 is using mdev for SF. I saw it yesterday and try to figure > > out the history. Since you are here, guess you know something 😊 > > > > [1] https://patchwork.ozlabs.org/project/netdev/cover/20191107160448.20962- > 1-pa...@mellanox.com/ > > [2] https://docs.mellanox.com/display/BlueFieldSWv25011176/Mediated+Devices > > Kernel maintainers rejected the use of mdev for this purpose > and suggested to use a real bus. > You can follow the discussion here: > https://lore.kernel.org/netdev/20191108205204.gb1277...@kroah.com/
OK. Thanks for the info. > > Does Intel plan to use mdev for SF? Yes. In our term it's called Assignable Device Interface (ADI) introduced in Intel Scalable IOV (https://01.org/blogs/2019/assignable-interfaces-intel-scalable-i/o-virtualization-linux) And vfio-mdev is chosen to be the software framework for it. I start to realize there is difference between SF and ADI: SF considers multi-function devices which may include net/regex/vdpa/... But ADI only focuses on the virtualization of the devices and splitting devices to logic parts and providing huge number of interfaces to host APP. I think SF also considers this but is mainly used for multi-function devices (like DPU in your term? Correct me if I'm wrong). And I also noticed that the mdev-based interface can only be used in userspace but aux-based interface can also be used by other kernel sub-system (like for net, wrap it as netdev). Thanks, Chenbo > > For the sake of follow-up discussion, this is the official mdev doc: > https://www.kernel.org/doc/Documentation/vfio-mediated-device.txt > >
