From mboxrd@z Thu Jan  1 00:00:00 1970
From: xiexiangyou <xiexiangyou@huawei.com>
Subject: [RFC]Enlarge the dalta of TSC match window from one second to five
 second
Date: Mon, 11 Aug 2014 15:41:00 +0800
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hi,

In kvm_write_tsc() func of kvm, The TSCs will be synchronized unless the time diff of creating vcpus small than one second.
However, In my enviroment, stress is large, the vcpu creating time is delay, sometimes the diff time between vcpu creating
is more than one second. In this case, TSCs in VM are not the same with each other when it boot.
(1)To solve the issue, should we enlarge the dalta of TSC match window from one second to five second?

as follows:

	 * it's better to try to match offsets from the beginning.
          */
-	if (nsdiff < NSEC_PER_SEC &&
+	if (nsdiff < 5 *NSEC_PER_SEC &&
	    vcpu->arch.virtual_tsc_khz == kvm->arch.last_tsc_khz) {
 		if (!check_tsc_unstable()) {

(2)Another way to solve the issue: setting all VPUs' tsc_offset equal to the first boot VCPU's. So in special case, hotpluging VCPU,
we can ensure TSC clocksource is stable.

Thanks.
xiexiangyou