Re: [Xen-devel] [PATCH 40/57] ARM: new VGIC: Add PRIORITY registers handlers

[Julien Grall <julien.grall@xxxxxxx>]

On 08/03/18 16:21, Andre Przywara wrote:
> Hi,
>
> On 08/03/18 15:48, Julien Grall wrote:
> > On 05/03/18 16:03, Andre Przywara wrote:
> > > The priority register handlers are shared between the v2 and v3
> > > emulation,
> > > so their implementation goes into vgic-mmio.c, to be easily referenced
> > > from the v3 emulation as well later.
> > > There is a corner case when we change the priority of a pending
> > > interrupt which we don't handle at the moment.
> > I don't believe it is a corner case. The spec (8.9.12 ARM IHI 0069d) says:
> >
> > "Implementations must ensure that an interrupt that is pending at the
> > time of the write uses either the old value or the new value and must
> > ensure that the interrupt is neither lost nor handled more than once.
> > The effect of the change must be visible in finite time."
> >
> > So the current implementation looks compliant to the spec.
> Interestingly the GICv2 spec doesn't mention anything at all related to
> that, at least not in the IPRIORITYR description.
>
> Anyway, are you saying that I should just change the commit message?
Yes.

> > > This is based on Linux commit dd238ec2b87b, written by Andre Przywara.
> > Using short commit ID is usually a pretty bad idea because it may not be
> > uniq. For instance, a git show on my Linux tree will not be able to find
> > it.
> Indeed somehow the commit ID is wrong.
> Linux recommends (at least) 12 digits when space is important, plus the
> commit title, if possible. But this is just for the records, so I just
> went with the shortened SHA.
Well, it is not only just for the records. It is also a way for us to 
know where it comes from so we can find for the 
signed-off-by/authorship. So we need to easily find the exact commit and 
therefore the e-mail addresses.
> Even if that clashes in the future, the
> first hit should be the one. The commit message stem should be the same
> as in Linux for those commits.
Why the first hit should be the one? It likely means another commit have 
similar sha1 and likely going to be the new one. And usually git show 
will tell you "ambiguous".
Cheers,

--
Julien Grall

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