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    SubjectRe: [PATCH 1/2] keep guest wallclock in sync with host clock
    On Wed, Sep 02, 2009 at 02:44:11PM +0300, Avi Kivity wrote:
    > On 09/01/2009 02:50 PM, Glauber Costa wrote:
    >> KVM clock is great to avoid drifting in guest VMs running ontop of kvm.
    >> However, the current mechanism will not propagate changes in wallclock value
    >> upwards. This effectively means that in a large pool of VMs that need accurate timing,
    >> all of them has to run NTP, instead of just the host doing it.
    >>
    >> Since the host updates information in the shared memory area upon msr writes,
    >> this patch introduces a worker that writes to that msr, and calls do_settimeofday
    >> at fixed intervals, with second resolution. A interval of 0 determines that we
    >> are not interested in this behaviour. A later patch will make this optional at
    >> runtime
    >>
    >> +
    >> +static void kvm_sync_wall_clock(struct work_struct *work)
    >> +{
    >> + struct timespec now;
    >> +
    >> + kvm_get_wall_ts(&now);
    >>
    >
    > What happens if we schedule here?
    hummm, I guess disabling preemption would be enough to make us safe here?

    >
    >> +
    >> + do_settimeofday(&now);
    >> + schedule_next_update();
    >> +}
    >> +
    >> +static __init int init_updates(void)
    >> +{
    >> + schedule_next_update();
    >> + return 0;
    >> +}
    >> +/*
    >> + * It has to be run after workqueues are initialized, since we call
    >> + * schedule_delayed_work. Other than that, we have no specific requirements
    >> + */
    >> +late_initcall(init_updates);
    >>
    >
    > Should this run on bare metal too?
    >
    > --
    > error compiling committee.c: too many arguments to function
    >


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