Re: [PATCH v4 2/4] xen/arm: Handle cases when hardware_domain is NULL

[Julien Grall <julien@xen.org>]

Hi,

On 14/04/2021 21:35, Stefano Stabellini wrote:
> On Wed, 14 Apr 2021, Luca Fancellu wrote:
>>> On 14 Apr 2021, at 14:45, Julien Grall <julien@xen.org> wrote:
>>>
>>> Hi Luca,
>>>
>>> On 14/04/2021 12:29, Luca Fancellu wrote:
>>>>> On 14 Apr 2021, at 12:16, Julien Grall <julien@xen.org> wrote:
>>>>>
>>>>> Hi Luca,
>>>>>
>>>>> On 14/04/2021 10:14, Luca Fancellu wrote:
>>>>>> Among the common and arm codebase there are few cases where
>>>>>> the hardware_domain variable is checked to see if the current
>>>>>> domain is equal to the hardware_domain, change this cases to
>>>>>> use is_hardware_domain() function instead. >
>>>>>> Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
>>>>>> ---
>>>>>> v4 changes:
>>>>>> - removed unneeded check for domain NULL from is_hardware_domain
>>>>>>    introduced in v3
>>>>>
>>>>> After this change, this patch is only avoid to open-code is_hardware_domain(). Although, it adds an extra speculation barrier.
>>>>>
>>>>> I am not against the change, however I think the commit message needs to updated to match what the patch is doing.
>>>>>
>>>>> Can you propose a new commit message?
>>>> Hi Julien,
>>>> Yes I agree, what about:
>>>> xen/arm: Reinforce use of is_hardware_domain
>>>> Among the common and arm codebase there are few cases where
>>>
>>> I would drop 'common' because you are only modifying the arm codebase.
>>>
>>>> the hardware_domain variable is checked to see if the current
>>>> domain is equal to the hardware_domain, change this cases to
>>>> use is_hardware_domain() function instead.
>>>
>>>
>>>> In the eventuality that hardware_domain is NULL, is_hardware_domain
>>>> will return false because an analysis of the common and arm codebase
>>>> shows that is_hardware_domain is called always with a non NULL
>>>> domain pointer.
>>>
>>> This paragraph seems to come out of the blue. I would drop it.
>>>
>>> How about:
>>>
>>> "
>>> There are a few places on Arm where we use pretty much an open-coded version of is_hardware_domain(). The main difference, is the helper will also block speculation (not yet implemented on Arm).
>>>
>>> The existing users are not in hot path, so blocking speculation would not hurt when it is implemented. So remove the open-coded version within the arm codebase.
>>> "
>>>
>>> If you are happy with the commit message, I will commit it the series tomorrow (to give an opportunity to Stefano to review).
>>>
>>
>> Hi Julien,
>>
>> Yes your version is much better, thank you very much!
> 
> It looks great, thanks for your work on this!

I have committed the series. Thanks for the work!

Cheers,

-- 
Julien Grall