Re: [077/103] KVM: x86: Fix SVM VMCB reset

From: Zachary Amsden
Date: Sat Oct 23 2010 - 09:49:08 EST


On 10/22/2010 11:51 PM, Michael Tokarev wrote:
22.10.2010 22:51, Greg KH wrote:
2.6.35-stable review patch. If anyone has any objections, please let us know.
------------------

From: Marcelo Tosatti<mtosatti@xxxxxxxxxx>

commit 58877679fd393d3ef71aa383031ac7817561463d upstream.

On reset, VMCB TSC should be set to zero. Instead, code was setting
tsc_offset to zero, which passes through the underlying TSC.
Not an objection, but shouldn't this and subsequent 078 "KVM: x86: Move
TSC reset out of vmcb_init" patches be applied to 2.6.32 too? The same
problem exists in 2.6.32, and the two patches allows an smp linux guest
to boot in there, or such a guest just hangs at boot. (078 patch needs
to be adjusted a bit for 2.6.32, since the code there is a bit different
and it does not apply correctly; but the change is trivial).


I concur, although it's possible the backport could go even further. The problem has existed for some time, but only because of recent changes to selection of default clocksource as well as host side changes has it become an issue.

Zach
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