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

Avi Kivity
2010-12-06T08:29:21Z

On 12/04/2010 03:30 PM, Anthony Liguori wrote:
> On 12/04/2010 02:13 AM, Avi Kivity wrote:
>> On 12/04/2010 12:45 AM, Anthony Liguori wrote:
>>>> hlt exiting doesn't leave vcpu in the halted state (since hlt has
>>>> not been executed). So currently we never see a vcpu in halted state.
>>>
>>>
>>> Right, you mean the guest activity state being halt.
>>>
>>> My understanding is that it just needs to be cleared on exception
>>> injection. Would could clear it at every vmentry but that would
>>> introduce a vmcs_read() to the fast path which is undesirable.
>>
>> Also need to skip the hlt instruction (by calling the emulator for
>> example).
>
> I wasn't sure about this. Don't you want EIP to point to the
> beginning of the instruction such that the exception will cause the
> instruction to restart?

An interrupt causes the HLT to complete execution. APF completion
counts as an interrupt in this case.

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