On 02/05/2017 23:36, Marcelo Tosatti wrote:
> In the masterclock enabled case, kvmclock_offset must be adjusted so
> that user_ns.clock = master_kernel_ns + kvmclock_offset (that is, the
> value set from KVM_SET_CLOCK is the one visible at system_timestamp).
>
> This way the guest clock:
>
> 1. Starts counting when KVM_SET_CLOCK executes.
> 2. With the value provided by userspace.
So this fixes rounding errors?
> - now_ns = get_kvmclock_ns(kvm);
> - kvm->arch.kvmclock_offset += user_ns.clock - now_ns;
> +
> kvm_gen_update_masterclock(kvm);
> + if (ka->use_master_clock) {
> + /*
> + * In the masterclock enabled case,
> + * kvmclock_offset must be adjusted so that
> + * user_ns.clock = master_kernel_ns + kvmclock_offset
> + * (that is, the value set from KVM_SET_CLOCK is the
> + * one visible at system_timestamp).
> + */
> + kvm->arch.kvmclock_offset = user_ns.clock -
> + ka->master_kernel_ns;
> +
This needs to hold ka->pvclock_gtod_sync_lock, I think.
> + kvm_for_each_vcpu(i, vcpu, kvm)
> + kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
kvm_gen_update_masterclock already does that, why did you move that to
before the assignment?
Paolo
