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Re: [Xen-devel] [PATCH 15/18] xen/arm: Resume memory management on Xen resume

On Tue, 13 Nov 2018, Julien Grall wrote:
> Hi,
> On 13/11/2018 01:36, Stefano Stabellini wrote:
> > On Mon, 12 Nov 2018, Julien Grall wrote:
> > > On 11/12/18 11:30 AM, Mirela Simonovic wrote:
> > We can turn this assembly code into a .macro, so that at least when we
> > get around to it, we just need to fix it one place. In fact, I noticed
> > that the code sequence right before "mmu_resumed" and the one right
> > after are both indentical to the ones head.S, it would be good to avoid
> > the duplication if possible.
> This does not address my concern. We want to have suspend/resume compliant to
> the Arm architecture (at least to our best knowledge). Hiding it in a
> macro/function is not going to make it compliant.
> Nobody wants its platform randomly crashing on suspend/resume because the Arm
> Arm was knowingly not followed. This is more critical than the boot one as we
> are going to call that more often. So what is the action plan to correctly
> resume memory management in this series?

My suggestion does not address your concern, but at least it limits the
spreading of errors code-wise.

It is only natural for a contributor to start from existing code to
write new code. It just happens that the existing code is broken, thus,
the new code is broken too. We can't really expect any different :)

If we want the contributor to fix this, given that the change is a
difficult modification to delicate assembly code, we need to provide
detailed documentation and/or sample code. Otherwise I can't see how it
can go well.

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