On Sat, Mar 25, 2023 at 9:14 PM jiangdongxu <jiangdongxu1@xxxxxxxxxx> wrote: > > vDPA devices allow high-performance devices in a virtual machine by > providing a wire-speed data path. These devices require a vendor-specific host > driver but the data path follows the virtio specification. > > The support for generic-vdpa device was recently added to qemu in v8.0.0-rc version. > https://gitlab.com/qemu-project/qemu/-/commit/b430a2bd2303b9940cc80ec746887f463a25fc5c > > This allows libvirt to support these deviecs regardless of device type. > Currently, libvirt supports vDPA network devices, We need a new solution > to support generic-vdpa devices. > > At present, we have considered several options. > > Solution A: > Add type vdpa under the hostdev device，the device xml looks like > <devices> > <hostdev mode='subsystem' type='vdpa'> > <source dev='/dev/vhost-vdpa-0'/> > </hostdev> > </devices> > This solution is recommended. This configuration requires only that the > device supports the vDPA framework, easy for future expansion and same > as the qemu solution design idea. I prefer this one, it's easier to implement and works for any type of virtio devices and vDPA parents > > Solution B: > The current libvirt mode is used to add vDPA devices under different devices. > device xml looks like: > network: > <devices> > <interface type='generic-vdpa'> > <source dev='/dev/vhost-vdpa-0'/> > </interface> > </devices> > > storage: > <devices> > <disk type='generic-vdpa’> > <source dev='/dev/vhost-vdpa-0'/> > </disk> > </devices> > > The network interface has the vdpa type. Therefore, a new type is required to > distinguish the "generic-vdpa" type. However, this method differentiates > device types, which is not convenient for the expansion of other types > of vDPA devices. Not recommended. This should be the way when we have dedicated block layer support for vhost-vDPA. Which seems not necessary for general vDPA devices. > > Solution C: > Referring to PCI passthrough, Add the driver type (appropriate vendor-specific driver) to the driver of the PCI device. > The unbind/bind of the vDPA device driver and the creation of VDPA device are implemented by libvirt. > device xml looks like: > <devices> > <hostdev mode='subsystem' type='pci' managed='yes'> > <driver name='vp-vdpa'/> > <source> > <address domain='0x0000' bus='0x04' slot='0x01' function='0x01'/> > </source> > </hostdev> > </devices> > This solution is related to the vendor-specific driver and supports only the vdpa created by the PCI device. > vdpa devices created in vduse mode are not supported. This solution is not universal and is not recommended. I agree, this requires PCI specific knowledge which defeats the goal of vDPA to be device agnostic. Thanks > > > What's your proposal?
