Re: [PATCH RFC V3 2/4] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks

[Raghavendra K T <raghukt@linux.vnet.ibm.com>]

On 12/08/2011 03:10 PM, Avi Kivity wrote:
> On 12/07/2011 06:46 PM, Raghavendra K T wrote:
>> On 12/07/2011 08:22 PM, Avi Kivity wrote:
>>> On 12/07/2011 03:39 PM, Marcelo Tosatti wrote:
>>>>> Also I think we can keep the kicked flag in vcpu->requests, no need
>>>>> for
>>>>> new storage.
>>>>
>>>> Was going to suggest it but it violates the currently organized
>>>> processing of entries at the beginning of vcpu_enter_guest.
>>>>
>>>> That is, this "kicked" flag is different enough from vcpu->requests
>>>> processing that a separate variable seems worthwhile (even more
>>>> different with convertion to MP_STATE at KVM_GET_MP_STATE).
>>>
>>> IMO, it's similar to KVM_REQ_EVENT (which can also cause mpstate to
>>> change due to apic re-evaluation).
>>>
>>
>> Ok, So what I understand is we have to either :
>> 1. retain current kick flag AS-IS but would have to make it migration
>> friendly. [I still have to get more familiar with migration side]
>> or
>> 2. introduce notion similar to KVM_REQ_PVLOCK_KICK(??) to be part of
>> vcpu->requests.
>>
>> So what would be better? Please let me know.
>>
>
> IMO, KVM_REQ.
>

Ok, 'll continue in this direction. Hmm I think now the race condition 
should be kept in mind, pointed by Marcello.