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SubjectRE: [PATCH v2 1/1] x86/hyperv: Initialize clockevents earlier in CPU onlining
Date
> From: Michael Kelley <mikelley@microsoft.com>
> Sent: Tuesday, November 12, 2019 5:12 PM
> ...
> @@ -190,14 +278,20 @@ void hv_stimer_free(void)
> void hv_stimer_global_cleanup(void)
> {
> int cpu;
> ...
> + /*
> + * hv_stime_legacy_cleanup() will stop the stimer if Direct
> + * Mode is not enabled, and fallback to the LAPIC timer.
> + */
> + for_each_present_cpu(cpu) {
> + hv_stimer_legacy_cleanup(cpu);
> }
> +
> + /*
> + * If Direct Mode is enabled, the cpuhp teardown callback
> + * (hv_stimer_cleanup) will be run on all CPUs to stop the
> + * stimers.
> + */
> hv_stimer_free();
> }

In the case of direct_mode_enabled == true: When hv_vmbus unloads,
vmbus_exit() -> hv_stimer_global_cleanup() -> hv_stimer_free() ->
cpuhp_remove_state() disables the direct mode timers.

This does not look symmetric since hv_stimer_alloc() is called before
hv_vmbus loads, but I suppose this is not a real issue because hv_vmbus
should never unload in practice. :-)

Tested-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>

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