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RE: [PATCH v2 07/24] xen/device-tree: Parse 'cpu-map' node for CPU topology exploration
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
- Date: Mon, 8 Jun 2026 04:29:09 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 08 Jun 2026 04:29:38 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHc8U+PsZhvkHY9vEqKRtt8NHnfGrYrBomAgAF93dCAADBuAIAHZqKQ
- Thread-topic: [PATCH v2 07/24] xen/device-tree: Parse 'cpu-map' node for CPU topology exploration
Hello,
> >>> +#include <xen/types.h>
> >>> +#include <xen/device_tree.h>
> >>> +
> >>> +struct cpu_topology {
> >>> + int thread_id;
> >>> + int core_id;
> >>> + int cluster_id;
> >>> + int package_id;
> >>
> >> Can any of these go negative? If not, "unsigned int" please. Iirc I said
> >> the
> >> same elsewhere on v1. Please apply such comments throughout the series.
> >
> > These members can actually be '-1' to represent a missing entry when
> parsing the Device Tree's
> > 'cpu-map' node.
>
> Yet that sentinel doesn't need to be -1, does it? Any unsigned value greater
> or
> equal to NR_CPUS will do, I suppose.
Ok, I will make then unsigned int.
> > Since I imported this directly from Linux kernel 7.0 (specifically from
> include/linux/arch_topology.h
> > and drivers/base/arch_topology.c), I would lean toward keeping them as 'int'
> to minimize
> > any divergence from the original Linux implementation.
>
> Linux is quite a bit more lax though with use of (appropriate) types.
I agree with you at this point.
Thank you,
Hirokazu Takahashi.
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