On Mon, Jun 16, 2025 at 2:39 PM Jiří Denemark <jdene...@redhat.com> wrote:
> On Mon, Jun 16, 2025 at 02:14:15 +0200, Hector Cao wrote: > > On Mon, Jun 2, 2025 at 3:23 PM Jiří Denemark <jdene...@redhat.com> > wrote: > > > So except for not having the right CPU model in the capabilities XML > > > (which is not a bug, but rather a known limitation), is there any other > > > issue? I believe the host CPU would be correctly reported as > > > SapphireRapids/GraniteRapids with both hle and rtm disabled in domain > > > capabilities XML. > > > > > > > > Yes, you are right, if rtm and hle features are available, Granite Rapids > > will be correctly reported by virsh capabilities > > if the MSR bug is fixed (please take a look at : > > > https://lists.libvirt.org/archives/list/devel@lists.libvirt.org/thread/XNOHU7PODTZVCX7ZQ2PBM7DRQRG2D6C7/ > > ) > > > > You are also right that this is not a bug but rather a known limitation. > > However, we are getting regular bug reports from users who are not aware > of > > this known limitation and > > are confused. I would think if we can offer a better experience and save > > time for everyone, It might be worth the > > effort, especially GraniteRapids would be the last CPU model affected by > > this issue. > > A better experience that would actually work would be allowing CPU > features to be shown as disabled in host capabilities. But unfortunately > we can't do that for compatibility reasons. The CPU description in host > capabilities does not include the "policy" attribute and adding it could > result in apps thinking disabled features are actually enabled (because > they don't know they should read an extra attribute). > > > If you still believe that this little effort is not useful, I would think > > I do. It would only fix a few specific cases, but the same issue could > happen with other (even existing) CPU models and different features too. > It just depends on the exact host CPU and even BIOS settings. > > > that we can tackle this issue by offering better documentation about > > this known limitation. What do you think ? We are thinking about > > documenting it on Ubuntu but do you think that we can do something > > more upstream ? > > Yes, this should be fixed by a documentation. It should definitely go > upstream (and any relevant downstream documentation as well) unless it's > already there or in case it's clear enough or not in the right place. > > Do you have in mind any upstream documentation place where we can add this kind of documentation ? I see this page https://wiki.libvirt.org/Libvirt_identifies_host_processor_as_a_different_model_from_the_hardware_documentation.html I think it can be a good candidate. What do you think ? I would help document it if you think that is ok. Hector. > Jirka > > -- Hector CAO Software Engineer – Partner Engineering Team hector....@canonical.com https://launc <https://launchpad.net/~hectorcao>hpad.net/~hectorcao <https://launchpad.net/~hectorcao> <https://launchpad.net/~hectorcao>
