Re: [PATCH] tools/kvm_stat: Fix kvm_exit filter name

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Gavin Shan <gshan@redhat.com> writes:

> On 12/10/19 7:45 PM, Vitaly Kuznetsov wrote:
>> Gavin Shan <gshan@redhat.com> writes:
>> 
>>> The filter name is fixed to "exit_reason" for some kvm_exit events, no
>>> matter what architect we have. Actually, the filter name ("exit_reason")
>>> is only applicable to x86, meaning it's broken on other architects
>>> including aarch64.
>>>
>>> This fixes the issue by providing various kvm_exit filter names, depending
>>> on architect we're on. Afterwards, the variable filter name is picked and
>>> applied through ioctl(fd, SET_FILTER).
>> 
>> Would it actually make sense to standardize (to certain extent) kvm_exit
>> tracepoints instead?
>> 
>
> Yes, It makes sense, but it's something for future if you agree. Besides,
> It seems that other kvm tracepoints need standardization either.

If we change kvm_stat the way you suggest we'll have reverse issues
after changing tracepoints fields: updated kvm_stat won't work with the
fixed kernel. I understand that kvm_stat doesn't have to work with
anything but the corresponding kernel tree and so we can change it back
in the same series, but wouldn't it be an unnecessary churn?

I'd suggest we standardize 'exit_reason' field name now just to fix the
immediate issue, it shouldn't be a big change, probably the same size as
this patch. Changing other tracepoints to match can be left for future
generations :-) What do you say?

-- 
Vitaly