Re: [PATCH v1] target/i386: Always set leaf 0x1f

[Xiaoyao Li]

On 7/31/2024 4:49 PM, John Levon wrote:
> On Wed, Jul 31, 2024 at 03:02:15PM +0800, Xiaoyao Li wrote:
>
> > > Windows does not expect 0x1f to be present for any CPU model. But if it
> > > is exposed to the guest, it expects non-zero values.
> >
> > Please fix Windows!
>
> A ticket has been filed with MSFT, we are aware this is a guest bug.
>
> But that doesn't really help anybody trying to use Windows right now.

For existing buggy Windows, we can still introduce "cpuid-0x1f-enforce" 
but not make it default on.

People want to boot the buggy Windows needs to opt-in it themselves via 
"-cpu xxx,cpuid-0x1f-enforce=on". This way, we don't have live migration 
issue and it doesn't affect anything.

> regards
> john