Re: KVM: x86: update masterclock when kvmclock_offset is calculated (v2)

[Gleb Natapov <gleb@redhat.com>]

On Tue, Aug 27, 2013 at 11:55:29PM -0300, Marcelo Tosatti wrote:
> 
> The offset to add to the hosts monotonic time, kvmclock_offset, is
> calculated against the monotonic time at KVM_SET_CLOCK ioctl time.
> 
> Request a master clock update at this time, to reduce a potentially
> unbounded difference between the values of the masterclock and
> the clock value used to calculate kvmclock_offset.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
Applied, thanks.

> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d21bce5..0a93354 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1457,6 +1457,29 @@ static void pvclock_update_vm_gtod_copy(struct kvm *kvm)
>  #endif
>  }
>  
> +static void kvm_gen_update_masterclock(struct kvm *kvm)
> +{
> +#ifdef CONFIG_X86_64
> +	int i;
> +	struct kvm_vcpu *vcpu;
> +	struct kvm_arch *ka = &kvm->arch;
> +
> +	spin_lock(&ka->pvclock_gtod_sync_lock);
> +	kvm_make_mclock_inprogress_request(kvm);
> +	/* no guest entries from this point */
> +	pvclock_update_vm_gtod_copy(kvm);
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm)
> +		set_bit(KVM_REQ_CLOCK_UPDATE, &vcpu->requests);
> +
> +	/* guest entries allowed */
> +	kvm_for_each_vcpu(i, vcpu, kvm)
> +		clear_bit(KVM_REQ_MCLOCK_INPROGRESS, &vcpu->requests);
> +
> +	spin_unlock(&ka->pvclock_gtod_sync_lock);
> +#endif
> +}
> +
>  static int kvm_guest_time_update(struct kvm_vcpu *v)
>  {
>  	unsigned long flags, this_tsc_khz;
> @@ -3806,6 +3829,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
>  		delta = user_ns.clock - now_ns;
>  		local_irq_enable();
>  		kvm->arch.kvmclock_offset = delta;
> +		kvm_gen_update_masterclock(kvm);
>  		break;
>  	}
>  	case KVM_GET_CLOCK: {
> @@ -5689,29 +5713,6 @@ static void process_nmi(struct kvm_vcpu *vcpu)
>  	kvm_make_request(KVM_REQ_EVENT, vcpu);
>  }
>  
> -static void kvm_gen_update_masterclock(struct kvm *kvm)
> -{
> -#ifdef CONFIG_X86_64
> -	int i;
> -	struct kvm_vcpu *vcpu;
> -	struct kvm_arch *ka = &kvm->arch;
> -
> -	spin_lock(&ka->pvclock_gtod_sync_lock);
> -	kvm_make_mclock_inprogress_request(kvm);
> -	/* no guest entries from this point */
> -	pvclock_update_vm_gtod_copy(kvm);
> -
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> -		set_bit(KVM_REQ_CLOCK_UPDATE, &vcpu->requests);
> -
> -	/* guest entries allowed */
> -	kvm_for_each_vcpu(i, vcpu, kvm)
> -		clear_bit(KVM_REQ_MCLOCK_INPROGRESS, &vcpu->requests);
> -
> -	spin_unlock(&ka->pvclock_gtod_sync_lock);
> -#endif
> -}
> -
>  static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
>  {
>  	u64 eoi_exit_bitmap[4];
> 

--
			Gleb.