RE: [PATCH v3 4/6] target/i386: add support for VMX FRED controls

[Li, Xin3]

On 7/6/2024 9:23 AM, Paolo Bonzini wrote:
> 
> 
> Il sab 6 lug 2024, 17:57 Li, Xin3 <xin3.li@intel.com 
> <mailto:xin3.li@intel.com>> ha scritto:
> 
>      >> The bits in the secondary vmexit controls are not supported, and
>     in general the same
>      >> is true for the secondary vmexit case.  I think it's better to
>     not include the vmx-entry-
>      >> load-fred bit either, and only do the vmxcap changes.
> 
>      > Right, we don't need it at all.
> 
>     Hi Paolo,
> 
>     We actually do need the following change for nested FRED guests to boot:
> 
>     diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>     index 227ee1c759..dcf914a7ec 100644
>     --- a/target/i386/cpu.c
>     +++ b/target/i386/cpu.c
>     @@ -1285,7 +1285,7 @@ FeatureWordInfo
>     feature_word_info[FEATURE_WORDS] = {
>                   NULL, "vmx-entry-ia32e-mode", NULL, NULL,
>                   NULL, "vmx-entry-load-perf-global-ctrl",
>     "vmx-entry-load-pat", "vmx-entry-load-efer",
>                   "vmx-entry-load-bndcfgs", NULL,
>     "vmx-entry-load-rtit-ctl", NULL,
>     -            NULL, NULL, "vmx-entry-load-pkrs", NULL,
>     +            NULL, NULL, "vmx-entry-load-pkrs", "vmx-entry-load-fred",
>                   NULL, NULL, NULL, NULL,
>                   NULL, NULL, NULL, NULL,
>               },
> 
>     Or do you think it's not the root cause?
> 
> 
> The patch is correct but is FRED supported in nested VMX? Or is it with 
> not yet merged patches?

The FRED KVM patchset has support for nested FRED, but not merged yet.

It's here:
https://lore.kernel.org/kvm/20240207172646.3981-1-xin3.li@intel.com/

Thanks!
    Xin