Re: [Qemu-devel] [PATCH 1/2] i386: remove the new CPUID 'PCONFIG' from Icelake-Server CPU model

[Robert Hoo]

On Thu, 2018-12-20 at 13:38 +0100, Paolo Bonzini wrote:
> On 20/12/18 01:18, Robert Hoo wrote:
> > On Wed, 2018-12-19 at 14:01 +0000, Daniel P. Berrangé wrote:
> > > On Wed, Dec 19, 2018 at 09:44:40PM +0800, Robert Hoo wrote:
> > > > Signed-off-by: Robert Hoo <address@hidden>
> > > > ---
> > > >  target/i386/cpu.c | 3 +--
> > > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > > > 
> > > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > > > index 677a3bd..b6113d0 100644
> > > > --- a/target/i386/cpu.c
> > > > +++ b/target/i386/cpu.c
> > > > @@ -2613,8 +2613,7 @@ static X86CPUDefinition
> > > > builtin_x86_defs[] =
> > > > {
> > > >              CPUID_7_0_ECX_AVX512VNNI |
> > > > CPUID_7_0_ECX_AVX512BITALG
> > > > > 
> > > > 
> > > >              CPUID_7_0_ECX_AVX512_VPOPCNTDQ |
> > > > CPUID_7_0_ECX_LA57,
> > > >          .features[FEAT_7_0_EDX] =
> > > > -            CPUID_7_0_EDX_PCONFIG | CPUID_7_0_EDX_SPEC_CTRL |
> > > > -            CPUID_7_0_EDX_SPEC_CTRL_SSBD,
> > > > +            CPUID_7_0_EDX_SPEC_CTRL |
> > > > CPUID_7_0_EDX_SPEC_CTRL_SSBD,
> > > >          /* Missing: XSAVES (not supported by some Linux
> > > > versions,
> > > >                  * including v4.1 to v4.12).
> > > >                  * KVM doesn't yet expose any XSAVES state save
> > > > component,
> > > 
> > > This was shipped in QEMU 3.1.0, so I don't think we can
> > > unconditionally
> > > remove it like this without breaking CPU model migration compat. 
> > > 
> > 
> > I think the sooner, the better. Take the time window that Icelake
> > CPU
> > model has just shipped with QEMU 3.1.0 and is not publicly/widely
> > used
> > yet.
> 
> We should still leave it in the 3.1 machine types.  I've just sent a
> patch to do the same with MPX.
> 
I took a look your patch of "Disable MPX support on named CPU models".
Seems you do the same as I do to PCONFIG. So you agree with my above
patch?:-)

I won't object that keep it in 3.1 machine type as you do to MPX.

> Paolo
>