Re: [PATCH v7 3/8] KVM: VMX: Detect Tertiary VM-Execution control when setup VMCS config

[Zeng Guang]

On 4/1/2022 6:41 AM, Sean Christopherson wrote:
> On Fri, Mar 04, 2022, Zeng Guang wrote:
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index c569dc2b9192..8a5713d49635 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -2422,6 +2422,21 @@ static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt,
> >   	return 0;
> >   }
> >   
> > +static __init int adjust_vmx_controls_64(u64 ctl_min, u64 ctl_opt,
> I slightly prefer controls64 over controls_64.  As usual, KVM is inconsistent as
> a whole, but vmcs_read/write64 omit the underscore, so we can at least be somewhat
> consistent within VMX.
>
> > +					 u32 msr, u64 *result)
> > +{
> > +	u64 allowed1;
> > +
> > +	rdmsrl(msr, allowed1);
> > +
> > +	/* Ensure minimum (required) set of control bits are supported. */
> > +	if (ctl_min & ~allowed1)
> Eh, just drop @ctl_min.  Practically speaking, there is zero chance tertiary
> controls or any other control of this nature will ever be mandatory.  Secondary
> controls would fall into the same boat, but specifying min=0 allows it to share
> helpers, so it's the lesser of evils.
>
> With the error return gone, this can be
>
>    static __init u64 adjust_vmx_controls64(u64 ctl_opt, u32 msr)
>    {
> 	u64 allowed;
>
> 	rdmsrl(msr, allowed);
>
> 	return ctl_opt & allowed;
>    }

Make sense. I will change it.  Thanks.


> Alternatively, we could take the control-to-modify directly and have no return,
> but I like having the "u64 opt = ..." in the caller.