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Re: [Xen-devel] Is: Wrap-up Was: VIRTIO - compatibility with different virtualization solutions

Il 10/03/2014 08:54, Daniel Kiper ha scritto:

After some email exchange it looks that there is no consensus how VRITIO
should work on Xen. There is some hand waiving and some preliminary tests
but it is not sufficient to take final decision and put all needed stuff
into upcoming VIRTIO specification release. However, it is certain that
any solution which will be chosen in upcoming future MUST not break Xen
security model, has a good performance and easily integrate with currently
existing solutions. Additionally, it looks that that some terms (e.g.
physical address) in VIRTIO specification shall be changed to something
which is more platform independent (e.g. handle). Although such changes
should not lead to changes in currently existing VIRTIO implementations.

Taking into account above mentioned things I state that more research
and development work is needed. I volunteer to lead this task. Hence
I would like to propose that VIRTIO-46 task (Verify that VIRTIO devices
could be implemented in Xen environment) should be opened and work on
it should be deferred (from formal POV but that does not mean that work
should be on hold in real) until next VIRTIO release. Additionally,
I would like to rise VIRTIO on Xen issue during Xen Hackathon 2014 and
in other avenues to discuss this with other stake holders of VIRTIO.


Thanks for your work about virtio.
For now xen uses virtio only with spice vdagent on hvm domUs (that use virtio-serial). Virtio net and disks xl implementation is esperimental and old: http://wiki.xen.org/wiki/Virtio_On_Xen Last year i did some test with virtio-net and I found one regression with qemu 1.6.

If can be useful some details from my old mails about:
Based on my tests about virtio:
- virtio-serial seems working out of box with windows domUs and also with xen pv driver, on linux domUs with old kernel (tested 2.6.32) is also working out of box but with newer kernel (tested >=3.2) require pci=nomsi to work correctly and works also with xen pvhvm drivers, for now I not found solution for msi problem, there are some posts about it. - virtio-net was working out of box but with recent qemu versions is broken due qemu regression, I have narrowed down with bisect (one commit between 4 Jul 2013 and 22 Jul 2013) but I unable to found the exact commit of regression because there are other critical problems with xen in the range. - I not tested virtio-disk and I not know if is working with recent xen and qemu version.

About msi problem with virtio, xen and recent linux kernel see here:

Recently I have not had time to test with qemu 2.
Certainly in the next few months I will further tests.
Let me know when there will be particular changesand Iwill test and try to help if possible.

Thanks for any reply.

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