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

[Julien Grall <julien@xxxxxxx>]

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@xxxxxxx> wrote:
> > >
> > > Hi Luca,
> > >
> > > On 14/04/2021 12:29, Luca Fancellu wrote:
> > > > > On 14 Apr 2021, at 12:16, Julien Grall <julien@xxxxxxx> 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@xxxxxxx>
> > > > > > ---
> > > > > > 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