Re: [PATCH v2] KVM: x86: reset lapic_timer.expired_tscdeadline at SET_LAPIC time

[Paolo Bonzini <pbonzini@redhat.com>]

On 20/06/2016 15:05, Marcelo Tosatti wrote:
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index ea306ad..89be6e9 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2991,6 +2991,7 @@ static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu,
>  {
>  	kvm_apic_post_state_restore(vcpu, s);
>  	update_cr8_intercept(vcpu);
> +	vcpu->arch.apic->lapic_timer.expired_tscdeadline = 0;
>  

I think this is not correct.  You have programmed the host timer to an
early value when kvm_apic_post_state_restore called start_apic_timer.

I think that:

1) post_state_restore should cancel the timer and clear
lapic_timer.pending before writing the registers, not afterwards.
lapic_timer.expired_tscdeadline can be cleared at the same time.

2) kvm_write_tsc should do the same and restart the timer afterwards.

Thanks,

Paolo