Hello everyone, With QEMU 8.2, guests that: - use SeaBIOS - use something different than "-cpu host" OR don't use "host-phys- bits=on" - have more than 2815 MB of RAM
have problems with their virtio devices and, hence, malfunction in
various ways (e.g., if they're using a virtio disk, they don't find it,
and the VM does not boot).
This broke all of a sudden, as soon as we updated QEMU to 8.2.0 in
openSUSE, and we got some bugreports about it. E.g., this one [1]
includes some logs and info, but I can provide more, if helpful.
I did try master (instead of 8.2, although it was master as of last
week), but the problem was still there.
I've then bisected it to SeaBIOS commit:
96a8d130a8c2e908e357ce62cd713f2cc0b0a2eb ("be less conservative with
the 64bit pci io window"). In fact, falling back to an earlier SeaBIOS
version, before that commit, or even just reverting it [1], solves the
issue.
UEFI guests seem not to be affected in any way, no matter amount of RAM
or CPU model (well, of course, since it's a SeaBIOS commit! :-D What I
mean is that there seems to be nothing in edk2 that induces the same
behavior).
A way of working this around (beside switching to UEFI or to cpu=host)
is to turn on host-phys-bits, e.g., with '<maxphysaddr
mode="passthrough"/>' in the XML.
It is, however, a bit impractical to have to do this for all the VMs
that one may have... Especially if they're a lot! :-)
I know that there have been issues and discussions (and they were also
related to virtio, I think) about these changes already. I don't know
if it's the same or a related problem but is there a way to avoid
having to ask people to change all their VMs' config?
Thanks and Regards,
Dario
[1] https://bugzilla.suse.com/show_bug.cgi?id=1219977
[2] well, I actually reverted a6ed6b701f0a57db0569ab98b0661c12a6ec3ff8
too, for convenience
--
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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