Re: Let's remove some deprecated stuff

[Eduardo Habkost]

+Jiri, +Daniel, +Igor

On Thu, Apr 29, 2021 at 11:59:41AM +0200, Markus Armbruster wrote:
[...]
> I'm not sure there's anything to remove here, but anyway, Peter Maydell:
> 

This one is mine.

There's no code to remove, but the intention is to eventually
change default_cpu_version to CPU_VERSION_LATEST on newer machine
types.

> 
>     Runnability guarantee of CPU models (since 4.1.0)
>     '''''''''''''''''''''''''''''''''''''''''''''''''
> 
>     Previous versions of QEMU never changed existing CPU models in
>     ways that introduced additional host software or hardware
>     requirements to the VM.  This allowed management software to
>     safely change the machine type of an existing VM without
>     introducing new requirements ("runnability guarantee").  This
>     prevented CPU models from being updated to include CPU
>     vulnerability mitigations, leaving guests vulnerable in the
>     default configuration.
> 
>     The CPU model runnability guarantee won't apply anymore to
>     existing CPU models.  Management software that needs runnability
>     guarantees must resolve the CPU model aliases using the
>     ``alias-of`` field returned by the ``query-cpu-definitions`` QMP
>     command.
> 
>     While those guarantees are kept, the return value of
>     ``query-cpu-definitions`` will have existing CPU model aliases
>     point to a version that doesn't break runnability guarantees
>     (specifically, version 1 of those CPU models).  In future QEMU
>     versions, aliases will point to newer CPU model versions
>     depending on the machine type, so management software must
>     resolve CPU model aliases before starting a virtual machine.

libvirt had no time to adapt to this yet.  As far as I
understand, they need the following series to be merged first so
they can more easily resolve the unversioned CPU model name
aliases:

https://lore.kernel.org/qemu-devel/20201013230457.150630-1-ehabkost@redhat.com

I need to rebase that series and resubmit.

-- 
Eduardo