Re: [PATCH v3] KVM: VMX: do not disable interception for MSR_IA32_SPEC_CTRL on eIBRS

[Jim Mattson]

On Wed, May 25, 2022 at 10:14 AM Jon Kohler <jon@xxxxxxxxxxx> wrote:
>
>
>
> > On May 25, 2022, at 1:04 PM, Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> >
> > On Fri, May 20, 2022, Jon Kohler wrote:
> >> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> >> index 610355b9ccce..1c725d17d984 100644
> >> --- a/arch/x86/kvm/vmx/vmx.c
> >> +++ b/arch/x86/kvm/vmx/vmx.c
> >> @@ -2057,20 +2057,32 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >>                      return 1;
> >>
> >>              vmx->spec_ctrl = data;
> >> -            if (!data)
> >> +
> >> +            /*
> >> +             * Disable interception on the first non-zero write, unless the
> >> +             * guest is hosted on an eIBRS system and setting only
> >
> > The "unless guest is hosted on an eIBRS system" blurb is wrong and doesn't match
>
> Ah right, thanks for catching that
>
> > the code.  Again, it's all about whether eIBRS is advertised to the guest.  With
> > some other minor tweaking to wrangle the comment to 80 chars...
>
> RE 80 chars - quick question (and forgive the silly question here), but how are you
> counting that? I’ve got my editor cutting at 79 cols, where tab size is accounted
> for as 4 cols, so the longest line on my side for this patch is 72-73 or so.

Tab stops are every 8 characters. :-)