Re: [PATCH 5/5] KVM: x86: Using TSC deadline may cause multiple interrupts by user writes

[Paolo Bonzini <pbonzini@redhat.com>]

Il 03/10/2014 00:10, Nadav Amit ha scritto:
> To solve this situation, ignore host initiated TSC deadline writes that do not
> change the deadline value.
> 
> Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
> ---
>  arch/x86/kvm/lapic.c | 7 ++++++-
>  arch/x86/kvm/lapic.h | 3 ++-
>  arch/x86/kvm/x86.c   | 2 +-
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index b8345dd..0bcf2e1 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1346,14 +1346,19 @@ u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu)
>  	return apic->lapic_timer.tscdeadline;
>  }
>  
> -void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu, u64 data)
> +void kvm_set_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu,
> +				   struct msr_data *msr_info)
>  {
>  	struct kvm_lapic *apic = vcpu->arch.apic;
> +	u64 data = msr_info->data;
>  
>  	if (!kvm_vcpu_has_lapic(vcpu) || apic_lvtt_oneshot(apic) ||
>  			apic_lvtt_period(apic))
>  		return;
>  
> +	if (msr_info->host_initiated && apic->lapic_timer.tscdeadline == data)
> +		return;
> +

Why do we have to check host_initiated?

Paolo