[PATCH] cpu_map: Add -noMPX models for x86 Icelake Server

[Peter Krempa]

On Mon, Aug 15, 2022 at 14:11:49 -0700, Lena Voytek wrote:
> Intel has removed MPX capabilities from 10nm Icelake CPUs[1], which is
> reflected by the new models through the line marking mpx as removed.
> 
> The original Icelake Server models have been left alone to avoid regressions.
> 
> This adds:
> -Icelake-Server-noMPX
> -Icelake-Server-noTSX-noMPX

I didn't find this model in qemu, so this looks like you are inventing a
new model in libvirt.

While I'm not libvirt's expert on CPUs, but as far as I know libvirt
does not invent our own CPU model names.

In case of the 'noTSX' versions they were present named in such way in
qemu. The only reason we keep them is historical, but in qemu such
naming was already deprecated.

> References:
> 
>     [1] Memory Protection Extensions support removal
>         https://www.intel.com/content/www/us/en/support/articles/000059823/processors.html
> 
> Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1978064
>        https://gitlab.com/libvirt/libvirt/-/issues/304

In this issue I've linked the appropriate qemu commit, but according to
the commit message it seems that the MPX feature was dropped just in
certain machine types.

This will most likely mean that libvirt will not be able to delete it
out of the definition, because we need to be able to preserve
compatibility and VM ABI.