Re: [Xen-devel] [PATCH V10 4/5] p2m: Always use hostp2m when clipping rangesets

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.12.18 at 13:18, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> Right, so you're saying that the series would be able to go in provided
> that the situation is not made worse than it currently is.

Well, I'm not the maintainer of this code, so in principle the
series can go in despite my reservations.

> As far as I can tell, the patch changes nothing functionally from the
> current state of affairs: when called for the hostp2m it behaves exactly
> the same.
> 
> The one difference is the early return, which is certainly not making
> things worse: rangeset_add_range() will crash the hypervisor in an
> ASSERT(start <= end). It just happened that that never occured for the
> hostp2m - so it will continue to not happen for the hostp2m.
> 
> Could you please provide more details on the case that is making things
> worse? Which cases of "start" (if that is what you mean) make things worse?

Okay, I've looked again - start indeed doesn't get clipped. Yet the
added return path plus the comment next to it still make the
situation worse imo, as they further the impression that the clipping
of end is correct. Or in other words, with the change it'll be less
visible that there's a (perhaps just theoretical, as said) bug here.
Hence my desire to get the bug addressed while this code is
being basically re-done anyway.

Jan



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