Re: [PATCH 1/2] KVM: LAPIC: Prevent setting the tscdeadline timer if the lapic is hw disabled

[Vitaly Kuznetsov]

Wanpeng Li <kernellwp@xxxxxxxxx> writes:

> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> Prevent setting the tscdeadline timer if the lapic is hw disabled.
>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
>  arch/x86/kvm/lapic.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 5bf72fc..4ce2ddd 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -2195,7 +2195,7 @@ void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
>  {
>  	struct kvm_lapic *apic = vcpu->arch.apic;
>  
> -	if (!lapic_in_kernel(vcpu) || apic_lvtt_oneshot(apic) ||
> +	if (!kvm_apic_present(vcpu) || apic_lvtt_oneshot(apic) ||
>  			apic_lvtt_period(apic))
>  		return;

Out of pure curiosity, what is the architectural behavior if I disable
LAPIC, write to IA32_TSC_DEADLINE and then re-enable LAPIC before the
timer was supposed to fire?

-- 
Vitaly