From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [qemu patch V4 2/2] kvmclock: reduce kvmclock difference on
 migration
Date: Mon, 12 Dec 2016 17:44:52 -0200
Message-ID: <20161212194451.GA20241@amt.cnet>
References: <20161210172148.361793326@redhat.com>
 <20161210172324.482367805@redhat.com>
 <20161212180105.GF3808@thinpad.lan.raisama.net>
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Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org,
        Dr David Alan Gilbert <dgilbert@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Juan Quintela <quintela@redhat.com>,
        Radim Krcmar <rkrcmar@redhat.com>
To: Eduardo Habkost <ehabkost@redhat.com>
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On Mon, Dec 12, 2016 at 04:01:05PM -0200, Eduardo Habkost wrote:
> On Sat, Dec 10, 2016 at 03:21:50PM -0200, Marcelo Tosatti wrote:
> [...]
> >  static void kvmclock_realize(DeviceState *dev, Error **errp)
> >  {
> >      KVMClockState *s = KVM_CLOCK(dev);
> >  
> > +    if (kvm_has_adjust_clock_stable()) {
> > +        s->clock_is_reliable = true;
> > +    }
> > +
> 
> This seems unnecessary, as kvmclock_vm_state_change() makes sure
> it is set at the same time as s->clock. Should we just remove it?

There is this initialization that goes from ~running -> running
which assumes its initialized:

static void kvmclock_vm_state_change(void *opaque, int running,
                                     RunState state)
{
    KVMClockState *s = opaque;
    CPUState *cpu;
    int cap_clock_ctrl = kvm_check_extension(kvm_state,
KVM_CAP_KVMCLOCK_CTRL);
    int ret;

    if (running) {
        struct kvm_clock_data data = {};
        uint64_t pvclock_via_mem = 0;

        /*
         * If the host where s->clock was read did not support reliable
         * KVM_GET_CLOCK, read kvmclock value from memory.
         */
        if (!s->clock_is_reliable) {
            pvclock_via_mem = kvmclock_current_nsec(s);
        }