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

Anthony Liguori
2010-12-06T16:21:22Z

On 12/06/2010 09:16 AM, Avi Kivity wrote:
> On 12/06/2010 05:07 PM, Anthony Liguori wrote:
>>> Not the user space one. The exit we're interested in is external
>>> interrupt, and that one isn't delivered to userspace.
>>>
>>> I guess you could have a loop
>>>
>>> 1: hlt
>>> jmp 1b
>>>
>>> and enter it programming a timer to something close, and examine the
>>> vcpu state afterwards. However you don't propagate the VMCS halted
>>> state to the corresponding kvm state, so there's no way to test it.
>>> (a minor bug in your patch)
>>
>>
>> The activity state doesn't get propagated at all to the kvm state.
>> Can we get into a non-zero activity state today (either SHUTDOWN or
>> WAIT_SIPI)?
>
> 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.

Regards,

Anthony Liguori