On Thu, 14 Jan 2021 14:25:04 +0800 Chenbo Xia <chenbo....@intel.com> wrote:
> This series introduces a new device abstraction called emudev for emulated > devices. A new library (librte_emudev) is implemented. The first emudev > driver is also introduced, which emulates Intel Adaptive Virtual Function > (iavf) as a software network device. > > This series has a dependency on librte_vfio_user patch series: > http://patchwork.dpdk.org/cover/86498/ > > Background & Motivation > ----------------------- > The disaggregated/multi-process QEMU is using VFIO-over-socket/vfio-user > as the main transport mechanism to disaggregate IO services from QEMU. > Therefore, librte_vfio_user is introduced in DPDK to accommodate > emulated devices for high performance I/O. Although vfio-user library > provides possibility of emulating devices in DPDK, DPDK does not have > a device abstraction for emulated devices. A good device abstraction will > be useful for applications or high performance data path driver. With > this consideration, emudev library is designed and implemented. It also > make it possbile to keep modular design on emulated devices by implementing > data path related logic in a standalone driver (e.g., an ethdev driver) > and keeps the unrelated logic in the emudev driver. > > Design overview > --------------- > > +---------------------------------------+ > | +---------------+ +-----------+ | > | | iavf_emudev |<-->| data path | | > | | driver | | driver | | > | +---------------+ +-----------+ | > | | | > | --------------------------- VDEV BUS | > | | | > | +---------------+ | > +--------------+ | | vdev: | | > | +----------+ | | | /path/to/vfio | | > | | Generic | | | +---------------+ | > | | vfio-dev | | | | | > | +----------+ | | | | > | +----------+ | | +----------+ | > | | vfio-user| | | | vfio-user| | > | | client | |<---|----->| server | | > | +----------+ | | +----------+ | > | QEMU/DPDK | | DPDK | > +--------------+ +---------------------------------------+ > > - Generic vfio-dev/vfio-user client/vfio-user server > Above concepts are all introduced in librte_vfio_user patch series: > http://patchwork.dpdk.org/cover/86498/ > > - vdev:/path/to/vfio. > It binds to vdev bus driver. The vdev device is defined by DPDK applications > through command line as '--vdev=emu_iavf, path=/path/to/socket' in > iavf_emudev > case. Parameters in command line include device name (emu_iavf) which is > used > to identify corresponding driver (in this case, iavf_emudev driver), > path=/path/to/socket which is used to open the transport interface to > vfio-user > client in QEMU/DPDK. > > - data path driver. > The data path handling is splited to another standalone driver for modular > design. > > Why not rawdev for emulated device > ---------------------------------- > Instead of introducing new class emudev, emulated device could be presented > as rawdev. > However, existing rawdev APIs cannot meet the requirements of emulated > device. There are > three API categories for emudev. They are emudev device lifecycle management, > backend > facing APIs, and emudev device provider facing APIs respectively. Existing > rawdev APIs > could only cover lifecycle management APIs and some of backend facing APIs. > Other APIs, > even if added to rawdev API are not required by other rawdev applications. > This looks interesting but there has been on further work on it for three years. I recommend that the patch be dropped for now and resubmitted if/when the vfio_user patches get accepted.
