Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v2)

Anthony Liguori
2010-12-06T16:33:56Z

On 12/06/2010 10:30 AM, Avi Kivity wrote:
> On 12/06/2010 06:21 PM, Anthony Liguori wrote:
>>> No, right now we intercept SHUTDOWN (and turn it back, in qemu, into
>>> a RESET), and we emulate all the SIPI stuff. We also intercepted
>>> HLT so we couldn't get that activity state either.
>>
>>
>> Ok, looks like I need to make this per-VM and use a CAP along with an
>> interface to enable it to ensure that userspace to ensure it gets
>> saved/restored appropriately. I'll rework it.
>
> Not really, it's not any different from the ordinary intercepted HLT.
> Put the halted state where we currently put it (hint: nowhere), and
> all is fine.
>
> So we have a minor bug that we don't save/restore HLT state (either
> emulated or "real" with your patch), that causes a spurious wakeup
> after live migration.

Fair enough. I certainly likes fixes that do nothing :-)

> Note for your respin, yield_on_hlt became __read_often again, so
> please make it __read_mostly.

Done.

Regards,

Anthony Liguori