Re: [PATCH] arm64/hugetlb: Reserve CMA areas for gigantic pages on 16K and 64K configs

Anshuman Khandual
2020-06-24T12:22:24Z

On 06/24/2020 03:15 PM, Robin Murphy wrote:
> On 2020-06-24 01:17, Anshuman Khandual wrote:
>>
>>
>> On 06/23/2020 10:10 PM, Robin Murphy wrote:
>>> On 2020-06-23 13:48, Anshuman Khandual wrote:
>>>>
>>>> On 06/23/2020 02:54 PM, kernel test robot wrote:
>>>>>      423        /*
>>>>>      424         * must be done after arm64_numa_init() which calls numa_init() to
>>>>>      425         * initialize node_online_map that gets used in hugetlb_cma_reserve()
>>>>>      426         * while allocating required CMA size across online nodes.
>>>>>      427         */
>>>>>    > 428        arm64_hugetlb_cma_reserve();
>>>>
>>>> Wrapping this call site with CONFIG_HUGETLB_PAGE solves the problem.
>>>
>>> ...although it might be nicer to include asm/hugetlb.h directly so that you can pick up the stub definition reliably.
>>
>> Including <asm/hugetlb.h> directly does not solve the problem and
>> <linux/hugetlb.h> is no better. arm64_hugetlb_cma_reserve() needs
>> protection wrt both CMA and HUGETLB_PAGE. Dropped HUGETLB_PAGE
>> assuming it should have been taken care as the stub itself was in
>> <asm/hugetlb.h>, which turns out to be not true.
>
> Sure, I wasn't suggesting that the implementation of the header itself wouldn't need tweaking - the point I was trying to get at is that it's preferable to have *either* a stub definition in an always-reachable header, *or* inline #ifdefs around the caller. Mixing both such that there are 3 or 4 possible combinations just isn't nice to maintain.
>

Makes sense, which one of these would be preferred instead.

1. Call site is protected with HUGETLB_PAGE and CMA
2. Definition is protected with CMA and HUGETLB_PAGE - in arch/arm64/mm/hugetlb.c
3. Declaration is in arch/arm64/include/asm/hugetlb.h (without any #ifdef)

OR

1. Definition is protected with CMA and HUGETLB_PAGE - in arch/arm64/mm/hugetlb.c
2. Stub definition and declaration with #ifdefs (HUGETLB_PAGE and CMA) in arch/arm64/mm/init.c
3. Call site is without any #ifdef