Anup Patel anup.patel@linaro.org writes:
Hi All,
How about having a generic Virtio-based machine for emulating a virtual desktop ?
I know folks have already thought about this and probably also tried something or other on this front but, it will be good to know the downsides.
Virtio-desktop can be a separate specification describing a virtual desktop. Of-course we cannot avoid few architecture dependent virtual devices in but the Virtio-desktop specification will try to keep minimum possible architecture dependent devices.
There's a lot of reasons why a pure PV machine type is a bad idea. Lots of people have enumerated them in this thread.
But let me mention some things that I think we don't have covered today with PV:
- Graphics. Yes, I know QXL exists but it's (a) dependent on PCI (b) lacks the ability to gracefully degrade making it hopelessly tied to spice.
- Input. PS/2 mouse provides relative input which sucks in guests. For absolute input, we have VMMouse which is x86-specific, USB tablets (which are expensive to emulate) or the spice mouse which is intimately tied to the full Spice stack.
- Guest interaction. Copy/paste, drag and drop, etc. In theory this is covered in spice agents but it's all again hopelessly tied to Spice which makes it non-portable.
So there's good work todo but it's almost certainly in working with the Spice community to try to make what they already have more accessible to non-x86 architectures.
Regards,
Anthony Liguori
As per our thoughts, a Virtio-desktop will have two kinds of devices:
- Architecture dependent devices: This devices will be emulated in-kernel
by architecture specific code of KVM or Xen or Some other hypervisor. a) Virtualized CPU b) Virtualized PIC (i.e. in-kernel architecture specific emulation of irqchip) c) Virtualized Timer (i.e. in-kernel architecture specific emulation of timer chip) 2. Architecture independent devices: This are Virtio-based devices which are usually required by a desktop virtual machine. a) Virtio-blk (storage) - Already available b) Virtio-net (network) - Already available c) Virtio-fb (display) - It seems some work has been already done for Virtio frame buffer but I did not find drivers/fb/virtio-fb.c in latest kernel (http://thread.gmane.org/gmane.comp.emulators.kvm.devel/42720) - Is Virtio-fb work still in-progress ?? d) Virtio-input (keyboard/mouse/multi-touch) - Currently not available - It will provide keyboard input events - It will provide mouse input events - It will provide multi-touch input events e) Virtio-power (reset/shutdown/enumeration) - It can provides info about the entire virtual machine including CPU, PIC, Timer, available Virtio devices, etc. - It can also provide CPU and Virtio-device hot-plugging - Its primary purpose would be to provide reset and shutdown of CPU and Virtio devices. - There will be only one instance of this device and its location will be fixed for each architecture.
The Virtio-desktop specification may also describe a recommended memory map of for each architecture.
Right now, only missing devices seems to be Virtio-fb, Virtio-input, and Virtio-power, which some of us are willing to take-up.
IMHO, If we have something like Virtio-desktop specification then all possible guest OSes can have support for it and different hypervisor can emulate it without worrying about guest support.
Best Regards, Anup