On Tue, Nov 24, 2020 at 08:21:52 +0100, daggs wrote:
> Greetings Martin,
>
> > Sent: Monday, November 23, 2020 at 4:08 PM
> > From: "Martin Kletzander" <mklet...@redhat.com>
> > To: "daggs" <da...@gmx.com>
> > Cc: "libvirt-usersredhat.com" <libvirt-users@redhat.com>
> > Subject: Re: image works in native but not in vm when cpu
> > mode='host-passthrough' is set
> >
> > I'm sorry to say that, but nobody else here provides expertise, maybe
> > extracting
> > the qemu command-lines from the logs and asking on qemu-users might be the
> > best
> > next step. Sorry I cannot help you more as I do not see anything immediately
> > obvious here.
> >
> > Martin
> >
>
> seems like it, thanks for the help, I'll try over the qemu-users ml.
Yes, that's the best option. In general, host-passthrough just does not
enable all features supported by the host CPU. Some features require
special handling in KVM and/or QEMU before they can be made visible to a
guest. If the code is missing, the corresponding features would just be
filtered out. And some features can only be enabled as long as you don't
ever want to migrate the VM to another host. Such features are only
enabled if you explicitly ask for them to be enabled. And of course,
even if a feature is enabled and the corresponding handling in QEMU/KVM
exists, there might be bugs in there. So talking to QEMU developers is
a good idea as they are often involved in the KVM part too.
BTW, the following XML can be used to enable the non-migratable features
on host-passthrough CPU:
<cpu mode='host-passthrough' migratable='off'/>
Not sure if it's going to help in your case, though.
Jirka
