Re: [PATCH v4 24/25] KVM: VMX: Cache MSR_IA32_VMX_MISC in vmcs_config

Sean Christopherson
2022-08-02T16:28:28Z

On Tue, Aug 02, 2022, Vitaly Kuznetsov wrote:
> Sean Christopherson <seanjc@google.com> writes:
>
> > On Thu, Jul 14, 2022, Vitaly Kuznetsov wrote:
> >> @@ -2613,6 +2614,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> >> if (((vmx_msr_high >> 18) & 15) != 6)
> >> return -EIO;
> >>
> >> + rdmsrl(MSR_IA32_VMX_MISC, misc_msr);
> >
> > Might make sense to sanitize fields that KVM doesn't use and that are not exposed
> > to L1. Not sure it's worthwhile though as many of the bits fall into a grey area,
> > e.g. all the SMM stuff isn't technically used by KVM, but that's largely because
> > much of it just isn't relevant to virtualization.
> >
> > I'm totally ok leaving it as-is, though maybe name it "unsanitized_misc" or so
> > to make that obvious?
>
> I couldn't convince myself to add 'unsanitized_' prefix as I don't think
> it significantly reduces possible confusion (the quiestion would be
> 'sanitized for what and in which way?') so a need for 'git grep' seems
> imminent anyway.

Yeah, no objection to leaving it alone. VMX_MISC is such an oddball MSR that it
practically comes with disclaimers anyways :-)