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[Xen-devel] Guest time and TSCs since changeset 17716

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Guest time and TSCs since changeset 17716
From: Frank Van Der Linden <Frank.Vanderlinden@xxxxxxx>
Date: Mon, 29 Dec 2008 10:23:52 -0700
Delivery-date: Mon, 29 Dec 2008 09:24:25 -0800
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Changeset 17716 provides monotonically increasing guest time for HVM domains, by using the per-domain pl_time structure. hvm_get_guest_time and hvm_set_guest_time were changed to use this. Previously, the guest time was stored directly in the TSC offset fields of the vmx/smv control structures.

Since pt_freeze_time and pt_thaw_time use hvm_get/set_guest_time, they now no longer freeze TSC time for a guest. So, for timer_mode 0, TSC time is no longer frozen when a VCPU is not running. Unless you're using opt_softtsc, in which TSC exactly tracks the per-domain values.

I have no love for timer_mode 0 (it has serious issues on SMP), but was this change intentional? Or am I perhaps missing something?

- Frank


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