Re: [Xen-devel] [PATCH V4 7/8] xen/arm64: increase MAX_VIRT_CPUS to 128 on arm64

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 29/05/15 17:45, Julien Grall wrote:
> On 29/05/15 17:41, Andrew Cooper wrote:
>> On 29/05/15 17:20, Julien Grall wrote:
>>> On 29/05/15 16:51, Julien Grall wrote:
>>>>> diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h
>>>>> index 3b23e05..817c216 100644
>>>>> --- a/xen/include/asm-arm/config.h
>>>>> +++ b/xen/include/asm-arm/config.h
>>>>> @@ -47,7 +47,11 @@
>>>>>  #define NR_CPUS 128
>>>>>  #endif
>>>>>  
>>>>> +#ifdef CONFIG_ARM_64
>>>>> +#define MAX_VIRT_CPUS 128
>>>>> +#else
>>>>>  #define MAX_VIRT_CPUS 8
>>>>> +#endif
>>> Looking to the last patch, the usage of MAX_VIRT_CPUS is now minimal.
>>> Can't finish to replace MAX_VIRT_CPUS to another corresponding value and
>>> drop the define?
>> You cant drop MAX_VIRT_CPUS (I tried this when introducing
>> max_domain_vcpus()). It is used for some conditional compilation in
>> common code.
> AFAICT only in the event channel code to avoid allocating memory when
> less than 64 vCPU is used.

Correct.

>
> Anyway, if we can drop it. I would add a check in domain_max_vcpus for
> safety.

It has a second use currently for auditing the dom0_max_vcpus parameter
(for both x86 and ARM), but could easily be replaced with a
max_domain_vcpus() call.

~Andrew

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