> > + void (*msr_intercept)(struct kvm_vcpu *vcpu, unsigned int msr,
> > + bool enable);
>
> This should be toggle_wrmsr_intercept(), or toggle_msr_intercept()
> with a paramter to control RDMSR vs. WRMSR.
Ok, I can do that.
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index 6450c8c44771..0306c7ef3158 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7784,6 +7784,15 @@ static __exit void hardware_unsetup(void)
> > free_kvm_area();
> > }
> >
> > +static void vmx_msr_intercept(struct kvm_vcpu *vcpu, unsigned int
> > msr,
> > + bool enable)
> > +{
> > + struct vcpu_vmx *vmx = to_vmx(vcpu);
> > + unsigned long *msr_bitmap = vmx->vmcs01.msr_bitmap;
> > +
> > + vmx_set_intercept_for_msr(msr_bitmap, msr, MSR_TYPE_W, enable);
> > +}
>
> Unless I overlooked a check, this will allow userspace to disable
> WRMSR interception for any MSR in the above range, i.e. userspace can
> use KVM to gain full write access to pretty much all the interesting
> MSRs. This needs to only disable interception if KVM had interception
> disabled before introspection started modifying state.
We only need to enable the MSR interception. We never disable it -
please see kvmi_arch_cmd_control_msr().
