Anup Patel <anup.pa...@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: > 1. 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
