Hyper-V is adding multiple low speed "speciality" synthetic devices. Instead of writing a new kernel-level VMBus driver for each device, make the devices accessible to user space through UIO-based uio_hv_generic driver. Each device can then be supported by a user space driver. This approach optimizes the development process and provides flexibility to user space applications to control the key interactions with the VMBus ring buffer. The new synthetic devices are low speed devices that don't support VMBus monitor bits, and so they must use vmbus_setevent() to notify the host of ring buffer updates. These new devices also have smaller ring buffer sizes which requires to add support for variable ring buffer sizes. Moreover, this patch series adds a new implementation of the fcopy application that uses the new UIO driver. The older fcopy driver and application will be phased out gradually. Development of other similar userspace drivers is still underway. Efforts have been made previously to implement this solution earlier. Here are the discussions related to those attempts: https://lore.kernel.org/lkml/1691132996-11706-1-git-send-email-ssengar@xxxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/lkml/1665575806-27990-1-git-send-email-ssengar@xxxxxxxxxxxxxxxxxxx/ https://lore.kernel.org/lkml/1665685754-13971-1-git-send-email-ssengar@xxxxxxxxxxxxxxxxxxx/ Saurabh Sengar (6): Drivers: hv: vmbus: Add utility function for querying ring size uio_hv_generic: Query the ringbuffer size for device uio_hv_generic: Enable interrupt for low speed VMBus devices tools: hv: Add vmbus_bufring tools: hv: Add new fcopy application based on uio driver Drivers: hv: Remove fcopy driver drivers/hv/Makefile | 2 +- drivers/hv/channel_mgmt.c | 7 +- drivers/hv/hv_fcopy.c | 427 ----------------------------- drivers/hv/hv_util.c | 12 - drivers/hv/hyperv_vmbus.h | 5 + drivers/uio/uio_hv_generic.c | 14 +- include/linux/hyperv.h | 1 + tools/hv/Build | 3 +- tools/hv/Makefile | 10 +- tools/hv/hv_fcopy_daemon.c | 266 ------------------ tools/hv/hv_fcopy_uio_daemon.c | 488 +++++++++++++++++++++++++++++++++ tools/hv/vmbus_bufring.c | 316 +++++++++++++++++++++ tools/hv/vmbus_bufring.h | 158 +++++++++++ 13 files changed, 988 insertions(+), 721 deletions(-) delete mode 100644 drivers/hv/hv_fcopy.c delete mode 100644 tools/hv/hv_fcopy_daemon.c create mode 100644 tools/hv/hv_fcopy_uio_daemon.c create mode 100644 tools/hv/vmbus_bufring.c create mode 100644 tools/hv/vmbus_bufring.h -- 2.34.1
