Bug 1241691

What's the advantage of using them?

get rid of USB tablet and keyboard we have today. Currently we have to have USB

(In reply to Yaniv Kaul from comment #2)
> What's the advantage of using them?

Drop USB emulation.

USB is expensive (in terms of cpu cycles), especially the older usb host adapters (uhci/ohci/ehci).

USB emulation is complex, so being able to drop this reduces the attack surface.

On x86 you can get away without usb already because you have the ps2 keyboard and can use spice agent instead of usb-tablet for mouse input events.

On ppc64 and aarch64 you'll need some keyboard though, and with virtio-keyboard you can drop usb-kbd (and usb-tablet for guests not using spice) together the usb host adapter.

While being at it (just to be sure, I think there is another bz for that already):  virtio-gpu support would be nice very useful too.  On aarch64 virtio-gpu is the only display adapter available.

(In reply to Gerd Hoffmann from comment #4)
> (In reply to Yaniv Kaul from comment #2)
> > What's the advantage of using them?
> 
> Drop USB emulation.
> 
> USB is expensive (in terms of cpu cycles), especially the older usb host
> adapters (uhci/ohci/ehci).
> 
> USB emulation is complex, so being able to drop this reduces the attack
> surface.
> 
> On x86 you can get away without usb already because you have the ps2
> keyboard and can use spice agent instead of usb-tablet for mouse input
> events.

You theoretically can, practically you have the USB redirector, so you still keep USB emulation, no?

> 
> On ppc64 and aarch64 you'll need some keyboard though, and with
> virtio-keyboard you can drop usb-kbd (and usb-tablet for guests not using
> spice) together the usb host adapter.
> 
> While being at it (just to be sure, I think there is another bz for that
> already):  virtio-gpu support would be nice very useful too.  On aarch64
> virtio-gpu is the only display adapter available.

Is there remoting available for it?

> You theoretically can, practically you have the USB redirector, so you still
> keep USB emulation, no?

Yes, for usb redirection you still need usb emulation.
But IIRC usb redirection is a per-guest option in ovirt?

Also note that with no usb device connected the guest will shutdown all usb bus activity, so the emulation cpu cycles are still saved as long as usb redirection is not actively used.

> > While being at it (just to be sure, I think there is another bz for that
> > already):  virtio-gpu support would be nice very useful too.  On aarch64
> > virtio-gpu is the only display adapter available.
> 
> Is there remoting available for it?

virtio-gpu can operate in two modes: 2d (not accelerated) and 3d (virgl acceleration).  2d mode works remotely just fine, like any other qemu display adapter.  remote support for 3d/virgl mode is still WIP upstream.

(In reply to Gerd Hoffmann from comment #6)
> > You theoretically can, practically you have the USB redirector, so you still
> > keep USB emulation, no?
> 
> Yes, for usb redirection you still need usb emulation.
> But IIRC usb redirection is a per-guest option in ovirt?

Yes, but do you expect the user to shutdown and restart the VM just to get it working? Michal - can you confirm?

> 
> Also note that with no usb device connected the guest will shutdown all usb
> bus activity, so the emulation cpu cycles are still saved as long as usb
> redirection is not actively used.
> 
> > > While being at it (just to be sure, I think there is another bz for that
> > > already):  virtio-gpu support would be nice very useful too.  On aarch64
> > > virtio-gpu is the only display adapter available.
> > 
> > Is there remoting available for it?
> 
> virtio-gpu can operate in two modes: 2d (not accelerated) and 3d (virgl
> acceleration).  2d mode works remotely just fine, like any other qemu
> display adapter.  remote support for 3d/virgl mode is still WIP upstream.

Michal - where do we stand on this?

(In reply to Yaniv Kaul from comment #7)
> (In reply to Gerd Hoffmann from comment #6)
> > > You theoretically can, practically you have the USB redirector, so you still
> > > keep USB emulation, no?
> > 
> > Yes, for usb redirection you still need usb emulation.
> > But IIRC usb redirection is a per-guest option in ovirt?
> 
> Yes, but do you expect the user to shutdown and restart the VM just to get
> it working? Michal - can you confirm?

yes. I do expect to restart VMs like with all hw-related changes in new cluster level. And yes, for enabling/disabling usb redirection you would need to power cycle - it's enabled currently for all guests implicitly and "activated" by virt-viewer. Having an option to get rid of the USB stack is compelling to real-time, server, compute, non-VDI use cases

> 
> > 
> > Also note that with no usb device connected the guest will shutdown all usb
> > bus activity, so the emulation cpu cycles are still saved as long as usb
> > redirection is not actively used.
> > 
> > > > While being at it (just to be sure, I think there is another bz for that
> > > > already):  virtio-gpu support would be nice very useful too.  On aarch64
> > > > virtio-gpu is the only display adapter available.
> > > 
> > > Is there remoting available for it?
> > 
> > virtio-gpu can operate in two modes: 2d (not accelerated) and 3d (virgl
> > acceleration).  2d mode works remotely just fine, like any other qemu
> > display adapter.  remote support for 3d/virgl mode is still WIP upstream.
> 
> Michal - where do we stand on this?

Played with it, not consumable yet. I do not expect to have all components ready before 7.4

This request has been proposed for two releases. This is invalid flag usage. The ovirt-future release flag has been cleared. If you wish to change the release flag, you must clear one release flag and then set the other release flag to ?.

This will not be addressed in a reasonable timeframe. Please re-open if it's still important.