Re: [PATCH v2 2/2] xen: implement VCPUOP_register_runstate_phys_memory_area

[Andrii Anisov <andrii.anisov@gmail.com>]

Hello Jan,

On 16.05.19 15:09, Jan Beulich wrote:
>>>> On 23.04.19 at 10:10, <andrii.anisov@gmail.com> wrote:
>> --- a/xen/include/xen/sched.h
>> +++ b/xen/include/xen/sched.h
>> @@ -163,15 +163,23 @@ struct vcpu
>>       void            *sched_priv;    /* scheduler-specific data */
>>   
>>       struct vcpu_runstate_info runstate;
>> +
>> +    spinlock_t      mapped_runstate_lock;
> 
> Besides other comments given elsewhere already - does this
> really need to be a per-vCPU lock? Guests aren't expected to
> invoke the API frequently, so quite likely a per-domain lock
> would suffice. Quite possibly domain_{,un}lock() could
> actually be (re-)used.

I'd not use a per-domain lock here. This lock will be locked on every runstate area update, what's happening on every context switch. And the event of simultaneous switching of vcpus from the same domain has quite high probability.

-- 
Sincerely,
Andrii Anisov.

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