On Wed, Feb 14, 2024 at 02:16:58PM +0100, Jiri Denemark wrote: > On Wed, Feb 14, 2024 at 13:23:09 +0100, Tim Wiederhake wrote: > > On Wed, 2024-02-14 at 12:39 +0100, Jiri Denemark wrote: > > > On Wed, Feb 14, 2024 at 12:07:46 +0100, Michal Prívozník wrote: > > > > On 2/9/24 11:52, Tim Wiederhake wrote: > > > > > The mpx feature was removed from the corresponding qemu cpu > > > > > models. > > > > > With mpx in the libvirt cpu models, libvirt believes the feature > > > > > to be implicitly enabled when creating qemu VMs, while in fact it > > > > > is > > > > > disabled. > > > > > > > > > > This became an issue when commit 94eacd5a5f introduced new vmx-* > > > > > features, of which some are dependent on mpx (see > > > > > "feature_dependencies" > > > > > table in qemu target/i386/cpu.c), e.g. vmx-exit-clear-bndcfgs and > > > > > vmx-entry-load-bndcfgs. These features cannot be enabled by qemu > > > > > without also mpx being enabled, leading to the error message > > > > > > > > > > error: Failed to create domain from testdomain.xml > > > > > error: operation failed: guest CPU doesn't match > > > > > specification: missing features: mpx,vmx-exit-clear-bndcfgs, > > > > > vmx-entry-load-bndcfgs > > > > > > > > > > when trying to create a VM with a "host-model" cpu on a host that > > > > > does support mpx and the mentioned vmx-* features: > > > > > > > > > > <domain> > > > > > ... > > > > > <cpu mode='host-model' check='full' /> > > > > > ... > > > > > </domain> > > > > > > > > > > Resolve the issue by removing mpx from libvirt's cpu models as > > > > > well. > > > > > > > > Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx> > > > > > > Hold on. I was trying to think whether this is safe for migrations, > > > but > > > have to act fast now. Could you please explain in the commit message > > > that nothing breaks during migration no matter what CPU configuration > > > is > > > used in a domain XML when migrating between all combinations of > > > libvirt > > > with/without this change? In case some configurations would be > > > refused > > > we need to make sure those are impossible to hit in real world. > > > > > > Jirka > > > > My knowledge about migration is limited, hence I am hesitant to make > > factual claims. That being said, my understanding is that by requesting > > e.g. a Skylake-Client cpu 'mpx' was never actually enabled in the VM as > > qemu's version of the same cpu model did not include that feature. > > Well, if our CPU model has mpx than QEMU must have had it too at some > point. The question is whether it was ever released. And also whether > the feature could have ever been enabled in any running domain or trying > to enable it caused the domain to fail to start anyway. QEMU CPUs originally had 'mpx', and it was later turned off by a 4.0 machine type versions. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| _______________________________________________ Devel mailing list -- devel@xxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxx
