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

[Xiaoyao Li]

On 8/1/2024 6:25 PM, Igor Mammedov wrote:
> On Thu, 1 Aug 2024 15:36:10 +0530
> Manish <manish.mishra@nutanix.com> wrote:
>
> > On 31/07/24 9:01 pm, Xiaoyao Li wrote:
> > > !-------------------------------------------------------------------|
> > >   CAUTION: External Email
> > >
> > > |-------------------------------------------------------------------!
> > >
> > > 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.
> >
> >
> > Yes, that makes sense, I will send a updated patch by tomorrow if no one
> > has any objection with this.
>
> I'd rename it to
>     x-have-cpuid-0x1f-leaf
> (x-) to reflect that it's not stable/maintained and subject
> to be dropped in future
>
> Also please clearly spell out that it's a temporary workaround for ...
> in commit message.

I have a patch at hand, to introduce enable_cpuid_0x1f similar as 
enable_cpuid_0xb, for TDX:

https://github.com/intel-staging/qemu-tdx/commit/de08fd30926bc9d7997af6bd12cfff1b998da8b7

It is not a temporary solution. So I would suggest to drop (x-).
If no objection, I think Manish can start from my patch and it only 
misses a property definition for windows case:

  DEFINE_PROP_BOOL("cpuid-0x1f", X86CPU, enable_cpuid_0x1f, false);



> > >   
> > > > regards
> > > > john
> >
> >
> > Thanks
> >
> > Manish Mishra