Re: [PATCH v5 untested] kvm: better MWAIT emulation for guests

Radim Krčmář
2017-04-04T13:44:46Z

[Cc qemu-devel as we've gone off-topic]

2017-04-04 15:15+0200, Alexander Graf:
> On 04/04/2017 03:13 PM, Radim Krčmář wrote:
>> 2017-04-04 14:51+0200, Alexander Graf:
>> > Please see my patch to force enable CPUID bits ;).
>> Nice. MWAIT could also use setting of arbitrary values for its leaf,
>> but a generic interface for that would probably look clunky on the
>> command line ...
>
>
> I think we should have an interface similar to smbios for that eventually.
> Something where you can explicitly set arbitrary CPUID leaf information
> using leaf specific syntax. There are more leafs where it would make sense -
> cache topology for example.

Right, separating cpuid from -cpu makes it bearable, like

-cpuid leaf=%x[,subleaf=%x][,eax=%x][,ebx=%x][,ecx=%x][,edx=%x]

And Having multiple interfaces for the same thing would result in some
corner case decisions ...
I think QEMU should check that feature flags specified flags specified
by -cpu are not cleared by -cpuid.
I'm not sure if setters like "|=" and "&=~" would be beneficial in some
cases.