Subject: Re: [PATCH V2 4/5] kvm/stats: Add provisioning for 64-bit vcpu statistics

From: Suraj Jitindar Singh <[email-masked]>
Date: Fri, 15 Jul 2016 17:52:20 +1000

On 14/07/16 19:42, Paolo Bonzini wrote:
>
> On 13/07/2016 20:00, Christian Borntraeger wrote:
>>>>>> I thought u64 still existed on 32-bit architectures. unsigned long
>>>>>> would be fine but with the caveat that certain stats would overflow on
>>>>>> 32-bit architectures.
>>>> Yes, but not all 32-bit architectures can do atomic read-modify-write
>>>> (e.g. add) operations on 64-bit values.
>> So what about only doing it for the VCPU events? Those should be only
>> modified by one CPU. We would have some odd values on 32bit overflow, but
>> this will be certainly better than just start with 0
> If that's good enough for PPC, that's fine.
>
> Paolo

I'm don't feel great about having vcpu_stats as u64 and vm_stats still as u32
it's just a bit inconsistent.

That being said, it's only the vcpu_stats which I require to be u64 at this
stage so it's possible to just upgrade those.