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Re: [Xen-devel] softtsc for PV guests
| To: | Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] softtsc for PV guests |
| From: | Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
| Date: | Fri, 21 Aug 2009 16:59:58 -0700 |
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On 08/21/09 16:31, Dan Magenheimer wrote:
> Enabling CR4_TSD only traps ring>0 rdtscs. Trapping guest kernel
> rdtsc's is ultimately necessary because the Linux kernel does NOT
> adequately handle all the possible changes in TSC characteristics
> that can occur if Xen moves an already booted guest from one
> physical machine to another (or even from one set of pcpus
> to another on certain physical machines). I recognize this
> is very ugly, but it may be the only way to guarantee
> correctness 100% of the time.
PV guests already correct for that by using the data Xen provides; they
don't require Xen to do any correction or synthesis of tsc values.
> The system is definitely not dead, but dom0 is busy looping or
> something. I can probably isolate the code, but the xen
> changes seem small enough that it's hard to believe they
> could cause this kind of problem.
>
'0' on the Xen console will tell you where its spinning. Oh, is it dom0
or domU?
J
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