On Sun, Feb 18, 2024 at 08:10:36AM +0100, Greg KH wrote: > On Sat, Feb 17, 2024 at 10:03:34AM -0800, Saurabh Sengar wrote: > > 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/ > > So is this a v4 of the patch series? What has changed from those > previous submissions? In the most recent attempt we introduced a new driver uio_hv_vmbus_client for slow devices, where as in this new approach we are making use of existing uio_hv_generic driver. We also introduced the function to query ring buffer sizes, this is an attempt to address your comment on earlier series to avoid kernel params. Comment ref: https://lore.kernel.org/lkml/Y0bipdisMbTNMYOq@xxxxxxxxx/ We later tried to have ring buffer sizes via sysfs for which we wrote a new driver uio_hv_vmbus_client as explained above. This is the next approach in an attempt to address all of the concerns with all the previous series. - Saurabh > > thanks, > > greg k-h
