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Re: [PATCH v2 03/17] xen/arm: implement node distance helpers for Arm
- To: Wei Chen <Wei.Chen@xxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 12 Jan 2023 09:11:19 +0100
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- Cc: nd <nd@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 12 Jan 2023 08:11:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.01.2023 07:31, Wei Chen wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@xxxxxxxx>
>> Sent: 2023年1月11日 0:47
>>
>> On 10.01.2023 09:49, Wei Chen wrote:
>>> --- a/xen/arch/arm/include/asm/numa.h
>>> +++ b/xen/arch/arm/include/asm/numa.h
>>> @@ -28,6 +28,20 @@ enum dt_numa_status {
>>> DT_NUMA_OFF,
>>> };
>>>
>>> +/*
>>> + * In ACPI spec, 0-9 are the reserved values for node distance,
>>> + * 10 indicates local node distance, 20 indicates remote node
>>> + * distance. Set node distance map in device tree will follow
>>> + * the ACPI's definition.
>>> + */
>>> +#define NUMA_DISTANCE_UDF_MIN 0
>>> +#define NUMA_DISTANCE_UDF_MAX 9
>>> +#define NUMA_LOCAL_DISTANCE 10
>>> +#define NUMA_REMOTE_DISTANCE 20
>>
>> In the absence of a caller of numa_set_distance() it is entirely unclear
>> whether this tying to ACPI used values is actually appropriate.
>>
>
> From Kernel's NUMA device tree binding, it seems DT NUMA are reusing
> ACPI used values for distances [1].
I can't find any mention of ACPI in that doc, so the example values used
there matching ACPI's may also be coincidental. In no event can a Linux
kernel doc serve as DT specification. If values are to match ACPI's, I
expect a DT spec to actually say so.
Jan
|
