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[Xen-devel] Time sources in Xen

  • To: xen-devel@xxxxxxxxxxxxxxxxxxx
  • From: Diwaker Gupta <diwaker.lists@xxxxxxxxx>
  • Date: Fri, 20 Jan 2006 11:12:57 -0800
  • Delivery-date: Fri, 20 Jan 2006 19:20:50 +0000
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  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>

I'm trying to figure out what time sources are exposed to Guests (not
dom0, just regular domU's) in Xen. In particular, I'm interesting in
x86 guests running Linux, which of the following time sources they
have access to, and whether these time sources are virtualized by Xen.
I'm trying to glean information from the source code, but I'm hoping
someone can give me a concise summary :)

o PIT: ?
o CMOS RTC/Time of Day: guests can read directly?
o Local APIC: only dom0 can read/write these via hypercalls. For
domU's the calls are ignored?
o ACPI timer: ?
o HPET: ?
o TSC: AFAIK guests can read the TSC in hardware?

Finally, have any of the above changed drastically between Xen 2.0 and Xen 3.x?

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