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Re: [PATCH v3 1/3] xen/device-tree: Parse 'cpu-map' node for CPU topology exploration
- To: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 1 Jul 2026 13:45:35 +0200
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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: Wed, 01 Jul 2026 11:45:44 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 01.07.2026 13:11, Hirokazu Takahashi wrote:
>>> +static unsigned int __init get_cpu_for_node(struct dt_device_node *node)
>>
>> Pointer-to-const?
>
> Do you mean this should be replaced with the following line?
> static unsigned int __init get_cpu_for_node(struct dt_device_node *const node)
No, that's a const pointer-to-something.
static unsigned int __init get_cpu_for_node(const struct dt_device_node *node)
>>> +#else /* CONFIG_CPU_TOPOLOGY */
>>> +
>>> +#define cpu_topology ((struct cpu_topology *)NULL)
>>
>> Why exactly is this needed? It very much looks as if its presence may hide
>> bugs.
>
> In the current code, the condition if ( cpu_topology ) is used to cover both
> cases:
> when CONFIG_CPU_TOPOLOGY is disabled, and when memory allocation for
> topology table fails.
>
> The next patch uses if ( cpu_topology ).
>
> static int setup_cpu_sibling_map(int cpu)
> {
> if ( !zalloc_cpumask_var(&per_cpu(cpu_sibling_mask, cpu)) ||
> !zalloc_cpumask_var(&per_cpu(cpu_core_mask, cpu)) )
> return -ENOMEM;
>
> if ( cpu_topology )
if ( IS_ENABLED(CONFIG_GENERIC_CPU_TOPOLOGY) )
Jan
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