Re: Correct format for HVM graphics

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Apr 04, 2012 at 05:08:30PM +0200, Stefan Bader wrote:
> Hi Stefano,
> 
> quite a while back in time, you and Konrad had a discussion about some HVM setup
> problems via libvirt. One part was graphics and the problem seemed to be that
> when creating a new instance through xend for HVM, the use of vfb was wrong. It
> mostly does work but then also defines a vkbd which takes a long time in the
> xenbus setup to finally fail.

So, this patch http://git.kernel.org/?p=linux/kernel/git/konrad/xen.git;a=commit;h=3066616ce23aad5719c23a0f21f32676402cb44b
fixes it in the kernel (and I remembered this time to stick stable@kernel.org on it).

It should eleviate some of the pains by making the timeout only 30 seconds when
vkbd is used, instead of the lengthy 6 minutes.

> 
> Because this was not a really fatal problem it did take a long time to actually
> get back to it. But now I had a look and found that libvirt indeed does use the
> vfb form for both the xen-xm and xen-sxpr formats (the latter being used to
> create guests). The decision is made based on the xend version number in the HVM
> case. Which would be wrong if I did understand your reply correctly.
> 
> I have been testing a patch to libvirt, which would not use a vfb definition
> whenever HVM is used (regardless of xend version). And it does seem to work (xm
> list -l however has a vfb device definition, but the same happens when creating
> the instance with a xm style config file that definitely has no vfb section in
> it). But I am testing based on our 12.04 release which uses Xen 4.1.2. So I want
> to make sure the solution for libvirt is correct for even the current Xen version.
> 
> So in short, is this always correct?
> 
> if (HVM or (PVM when xend is from xen < 3.0.4 / xend version < 3))
>    do not define a vfb device
> else /* PVM and xend version >= 3 */
>    define a vfb device
> 
> Thanks,
> Stefan
>