Re: [PATCH RFC V3 2/3] kvm: Note down when cpu relax intercepted or pause loop exited

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

On 07/13/2012 07:24 PM, Srikar Dronamraju wrote:
>> On 12/07/12 21:18, Raghavendra K T wrote:
>>> +#ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
>> [...]
>>> +	struct {
>>> +		bool cpu_relax_intercepted;
>>> +		bool dy_eligible;
>>> +	} ple;
>>> +#endif
>> [...]
>>>   	}
>>>   	vcpu->run = page_address(page);
>>> +	vcpu->ple.cpu_relax_intercepted = false;
>>> +	vcpu->ple.dy_eligible = false;
>>
>> This struct is only defined if CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT is set, but here it
>> is always accessed. Will break on !x86&&  !s390.
>
> How about moving this struct definition outside the CONFIG.
> i.e it would be available by default.
> If any arch cares to use vcpu_on_spin(), they would get the benefit by
> default.
>
> This would avoid all the CONFIG magic that we would have to do
> otherwise.
>

Okay, after discussing with Christian,
- even if ppc uses vcpu_on spin we will still be left with ia64 (though
broken currently) and arm (is on way).
- those who want to opt-out of this optimization but still wish to use
vcpu_spin, we have flexibility.

So with that in mind I am spinning V4 with
CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT. Let us see how it goes.