On 14/11/2016 15:52, Radim Krčmář wrote:
> The hunk below should return the same value in pvclock_ns and kernel_ns
> if they can be used interchangeably. boot_ns is expected to be a bit
> delayed, because it is read late. boot_ns shows a bounded offset from
> kernel_ns, unlike the drifting pvclock_ns.
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 83990ad3710e..30d4d3d02ac7 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6653,6 +6653,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> goto cancel_injection;
> }
>
> + if (vcpu->kvm->arch.use_master_clock) {
> + s64 kernel_ns;
> + cycle_t tsc_now, pvclock_ns, boot_ns;
> +
> + kvm_get_time_and_clockread(&kernel_ns, &tsc_now);
> + pvclock_ns = __pvclock_read_cycles(&vcpu->arch.hv_clock,
> kvm_read_l1_tsc(vcpu, tsc_now)) - vcpu->kvm->arch.kvmclock_offset;
> + boot_ns = ktime_get_boot_ns();
> +
> + printk("ns diff: %lld %lld\n", pvclock_ns - kernel_ns, boot_ns
> - kernel_ns);
> + }
> +
> preempt_disable();
>
> kvm_x86_ops->prepare_guest_switch(vcpu);
Ok, I'll post a v2 of this patch.
Paolo
