On Mon, Jun 11, 2018 at 05:50:30PM -0300, Eduardo Habkost wrote:
[...]
> > + /* TOPOEXT feature requires 0x8000001E */
> > + if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) {
> > + x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001E);
> > + }
>
> I suggest moving this hunk to a separate patch. I'm not 100%
> sure yet if this will require compat_props code to disable
> auto-xlevel-increase on older machine-types.
The problem here is that:
$QEMU -machine pc-i440fx-1.3 -cpu Opteron_G4,+topoext
currently results in xlevel=0x8000001A, since QEMU 1.3.
(The same applies to all machine-types between 1.3 and 2.12)
I was hoping that we could declare topoext as non-migration-safe,
but I believe libvirt will already include "topoext" when using
"host-model" if the host CPU supports TOPOEXT. Jiri, can you
confirm that?
We can address that with a "x-topoext-auto-xlevel" property, set
to true on all CPU models by default, and disabled by
PC_COMPAT_2_12.
The code would become:
if (cpu->topoext_auto_xlevel && env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) {
x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001E);
}
Or, we could simply declare that "-cpu Opteron_G4,+topoext" will
never increase xlevel automatically (on any machine-type), and
change the code above to:
if (cpu->auto_topoext && env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) {
x86_cpu_adjust_level(cpu, &env->cpuid_min_xlevel, 0x8000001E);
}
--
Eduardo
