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RE: [PATCH v4 09/17] xen/arm: introduce a helper to parse device tree NUMA distance map
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Wed, 26 Apr 2023 06:29:51 +0000
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- Cc: Wei Chen <Wei.Chen@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Wed, 26 Apr 2023 06:30:17 +0000
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- Thread-topic: [PATCH v4 09/17] xen/arm: introduce a helper to parse device tree NUMA distance map
Hi Jan,
> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Subject: Re: [PATCH v4 09/17] xen/arm: introduce a helper to parse device
> tree NUMA distance map
>
> > + distance = dt_next_cell(1, &matrix);
>
> Upon second thought I checked what dt_next_cell() returns: You're silently
> truncating here and then ...
>
> > + /* Bi-directions are not set, set both */
> > + numa_set_distance(from, to, distance);
> > + numa_set_distance(to, from, distance);
>
> ... here again. Is that really the intention?
By hunting down the historical discussions I found that using dt_next_cell() is
what Julien suggested 2 years ago in the RFC series [1]. Given the truncation
here is for node id (from/to) and distance which I am pretty sure will not
exceed 32-bit range, I think the silent truncation is safe.
However I understand your point here, the silent truncation is not ideal, so
I wonder if you have any suggestions to improve, do you think I should change
these variables to u64 or maybe I need to do the explicit type cast or any
better suggestions from you? Thanks!
[1] https://lists.xenproject.org/archives/html/xen-devel/2021-08/msg01175.html
Kind regards,
Henry
>
> Jan
|
