Re: [Xen-devel] [PATCH V3 1/2] x86/vm_event: added hvm/vm_event.{h, c}

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.05.17 at 16:42, <tamas@xxxxxxxxxxxxx> wrote:
> On Thu, May 4, 2017 at 11:37 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 04.05.17 at 17:17, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>> On 05/04/17 17:57, Tamas K Lengyel wrote:
>>>> On Thu, May 4, 2017 at 5:22 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>>>>> On 04.05.17 at 11:14, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>>>>> On 05/04/17 12:11, Jan Beulich wrote:
>>>>>>>>>> On 04.05.17 at 11:00, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>>>>>>> Created arch/x86/hvm/vm_event.c and include/asm-x86/hvm/vm_event.h,
>>>>>>>> where HVM-specific vm_event-related code will live. This cleans up
>>>>>>>> hvm_do_resume() and ensures that the vm_event maintainers are
>>>>>>>> responsible for changes to that code.
>>>>>>>>
>>>>>>>> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>>>>>>> Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
>>>>>>>
>>>>>>> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>>>>>>> albeit I wonder ...
>>>>>>>
>>>>>>>> +void hvm_vm_event_do_resume(struct vcpu *v)
>>>>>>>> +{
>>>>>>>> +    struct monitor_write_data *w;
>>>>>>>> +
>>>>>>>> +    if ( likely(!v->arch.vm_event) )
>>>>>>>> +        return;
>>>>>>>
>>>>>>> ... whether this now wouldn't better be an ASSERT().
>>>>>>
>>>>>> I have no objections (can this be done on commit or should I re-send 
>>>>>> V4?).
>>>>>
>>>>> Let's first see what Tamas thinks. If he agrees, I see not problem
>>>>> doing the adjustment while committing.
>>>>
>>>> I'm not quite sure how converting that to an ASSERT would work. It
>>>> looks fine to me as is tbh.
>>>
>>> I think Jan means that, since currently the only caller is
>>> hvm_do_resume() where there's already that check now (to avoid the
>>> call), we could here simply replace the if() with
>>> ASSERT(v->arch.vm_event). I could be wrong. :)
>>
>> You aren't - that's precisely my reasoning.
> 
> So if we are changing this to an ASSERT here then a check needs to be
> added on the caller site. That would work for me.

I don't follow - the reason I did ask for converting the if() here
was because (upon my request) a check in the caller has been
added (or actually, is being kept from the original code instead
of deleting it) in this version.

Jan


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