Hi On Tue, Mar 16, 2021 at 11:33 PM Dr. David Alan Gilbert <dgilb...@redhat.com> wrote:
> * Philippe Mathieu-Daudé (phi...@redhat.com) wrote: > > On 3/16/21 6:21 PM, Dr. David Alan Gilbert wrote: > > > Hi, > > > I've got a half-baked idea, which I thought might be worth > mentioning. > > > > > > How hard would it be to give qemu a usbredir server rather than client? > > > It would have nothing guest visible but would look logically like the > > > front (?) half of a usb interface; then you could use all of the > > > existing qemu emulated and passthrough device code, to build a usb > > > hierarchy and present it to a remote qemu. > > > > > > You'd get the ability to do emulated USB CDROM/storage, audio, network > > > and the glue for host USB connection (and smart cards??) - all in one > > > client that you can then use for connecting to a remote qemu. > > > > > > The next step of that is to make something analogous to a > > > qemu-storage-daemon, but for USB, so you have something that can > > > do all that USB stuff without actually having any processors. > > > > > > The even crazier step would then be to add a VNC client, and then you > > > have an almost complete remote client. > > > > Similarly to the out-of-process feature (on the same host)? > > Are you also interested in remote use (different host)? > > I was mainly interested in it for remote access; but potentially this > provides a clean break point to move all of the USB device emulation > into one separate process. > > It's an idea I suggested a few times too, once at least during 2017 KVM Forum multi-process talk, & when it was decided to implement usb CD emulation in spice-gtk (which I wish would use existing qemu code instead, or the NBD server I implemented initially, long time ago..). So yup, I'd like to see this happen too eventually. However it's not so attractive imho, you rather want virtio/vhost-user and for other devices you don't have a choice I'd focus on vfio-user. At some point hopefully, qemu should be able to provide a usb controller via vfio-user if you need it.
