Re: [Qemu-devel] [PATCH 6/6] qapi: discriminate CpuInfo[Fast] on SysEmuTarget, not CpuInfoArch

[Markus Armbruster <armbru@redhat.com>]

Eric Blake <eblake@redhat.com> writes:

> On 04/26/2018 09:34 AM, Markus Armbruster wrote:
>>>
>>> Acerbic discovery of the day: @CpuInfoArch has "x86", while configure
>>> produces:
>>>
>>>   TARGET_NAME  TARGET_BASE_ARCH
>>>          i386              i386
>>>        x86_64              i386
>>>
>>> Note how "i386" does not match "x86".
>> 
>> Review fail.
>> 
>> Just three weeks ago, we could still have fixed query-cpus-fast...
>
> Actually, I think we still can.  We already documented in the 2.12
> release notes that the "arch" field of query-cpus-fast is known to be
> broken for all but "s390x" (which is really the only arch field that
> MUST be correct, as that is the only time we send additional
> information).  And introspection can easily see both the enum contents
> (if we add something) as well as any other additions to the
> query-cpus-fast output union (although that is less likely), to use
> those as a witness for whether qemu is new enough to have fixed the
> bogus "arch" values.  I'd argue that if we change things right now, with
> intent to include the change in 2.12.1, before people start relying on
> the bogus "arch" of 2.12, then we should feel free to make
> query-cpus-fast output whatever we want for all architectures other than
> "s390x", even if it changes the current output of "x86".

In other words, we managed to screw up query-cpus-fast sufficiently to
let us fix it even now.  Cool, let's do it!