Re: [Qemu-devel] [PATCH 2/2] i386: Add some MSR based features on Cascadelake-Server CPU model

[Tao Xu]

On 1/15/2019 2:35 AM, Eduardo Habkost wrote:
> Sorry, we do have a problem here:
>
> On Thu, Dec 27, 2018 at 10:43:04AM +0800, Tao Xu wrote:
> [...]
> >   #define PC_COMPAT_3_0 \
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 09706ad51a..5296c73cd5 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -2499,7 +2499,8 @@ static X86CPUDefinition builtin_x86_defs[] = {
> >               CPUID_7_0_ECX_PKU | CPUID_7_0_ECX_OSPKE |
> >               CPUID_7_0_ECX_AVX512VNNI,
> >           .features[FEAT_7_0_EDX] =
> > -            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 |
> > +            CPUID_7_0_EDX_ARCH_CAPABILITIES,
>
> CPUID_7_0_EDX_ARCH_CAPABILITIES is still set on
> unmigratable_flags.  We need to make it migratable before adding
> it by default to a named CPU model.
Hi Eduardo,

Do you mean I need to remove CPUID_7_0_EDX_ARCH_CAPABILITIES
from .migratable_flags? Or CPUID_7_0_EDX_ARCH_CAPABILITIES can not
support migration now?

> Also, why are you setting this only on Cascadelake-Server and not
> on all the other Intel CPUs?
Thank you for your notice. I reviewed the git log of KVM.
"MSR_IA32_ARCH_CAPABILITIES is emulated in kvm, there is no dependency 
on hardware support for this feature". So do you mean we should also add 
features based on ARCH_CAPABILITIES in former CPU(such as skylake)?

> I'm queueing only patch 1/2 until we sort this out.