Re: [PATCH v6 8/8] kvm: vmx: virtualize split lock detection

[Xiaoyao Li]

On 3/25/2020 8:40 AM, Thomas Gleixner wrote:
> Xiaoyao Li <xiaoyao.li@xxxxxxxxx> writes:
> > +static inline bool guest_cpu_split_lock_detect_on(struct vcpu_vmx *vmx)
> > +{
> > +	return vmx->msr_test_ctrl & MSR_TEST_CTRL_SPLIT_LOCK_DETECT;
> > +}
> > +
> >   static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> >   {
> >   	struct vcpu_vmx *vmx = to_vmx(vcpu);
> > @@ -4725,12 +4746,13 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
> >   	case AC_VECTOR:
> >   		/*
> >   		 * Reflect #AC to the guest if it's expecting the #AC, i.e. has
> > -		 * legacy alignment check enabled.  Pre-check host split lock
> > -		 * support to avoid the VMREADs needed to check legacy #AC,
> > -		 * i.e. reflect the #AC if the only possible source is legacy
> > -		 * alignment checks.
> > +		 * legacy alignment check enabled or split lock detect enabled.
> > +		 * Pre-check host split lock support to avoid further check of
> > +		 * guest, i.e. reflect the #AC if host doesn't enable split lock
> > +		 * detection.
> >   		 */
> >   		if (!split_lock_detect_on() ||
> > +		    guest_cpu_split_lock_detect_on(vmx) ||
> >   		    guest_cpu_alignment_check_enabled(vcpu)) {
>
> If the host has split lock detection disabled then how is the guest
> supposed to have it enabled in the first place?

It is ||

Thanks,
-Xiaoyao