On Thu, Sep 15, 2022 at 11:00:29AM -0700, Lena Voytek wrote: > Sorry for the delayed response. > > On Wed, 2022-08-17 at 14:13 +0200, Jiri Denemark wrote: > > On Tue, Aug 16, 2022 at 06:38:59 -0700, Lena Voytek wrote: > > > With the current setup, a 10nm Icelake CPU, such as the Intel Xeon > > > Gold > > > 6338, will be incorrectly recognized by libvirt as a 14nm broadwell > > > CPU due > > > to the mpx label. See > > > https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1978064. > > > > Right, but what actual issue is this causing? The CPU model in host > > capabilities is not used for anything by libvirt. The CPU model shown > > in > > domain capabilities (virsh domcapabilities) is the one used by > > libvirt > > and it should correctly show Icelake-Server. > > The main issue being caused is that end users are unable to deploy > systems using libvirt without modification to x86_Icelake-Server- > noTSX.xml on 10nm Icelake. Having an additional definition that > specifies noMPX, similar to noTSX, would make the deployment process > much more convenient. This fix allows software such as OpenStack to > work by default on these systems. On the QEMU side, after the Spectre debacle, anticipating a never ending stream of further CPU flaws, we decided that adding new CPU variants with further "-xxxx" suffixes was not a sustainable idea. Thus QEMU introduced the idea of versioning CPUs, where a bare 'Icelake-Server' CPU would have multiple versions, each with distinct set of flags. The idea was that if the user requested 'Icelake-Server', libvirt should expand it to the best Icelake-Server-vNN version that matched the host the VM was launched on. Users would not need to care about versions, unless they wished to pick a specific version for live migration compat reasons. It is unfinished work on the libvirt side to do this automatic expansion and handling of versioned CPUs. 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 :|
