Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx> writes:
> On 04/17/2017 10:44 PM, Aneesh Kumar K.V wrote:
>> POWER9 supports hugepages of size 2M and 1G in radix MMU mode. This patch
>> enables the usage of 1G page size for hugetlbfs. This also update the helper
>> such we can do 1G page allocation at runtime.
>>
>> Since we can do this only when radix translation mode is enabled, we can't use
>> the generic gigantic_page_supported helper. Hence provide a way for architecture
>> to override gigantic_page_supported helper.
>>
>> We still don't enable 1G page size on DD1 version. This is to avoid doing
>> workaround mentioned in commit: 6d3a0379ebdc8 (powerpc/mm: Add
>> radix__tlb_flush_pte_p9_dd1()
>>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
>> ---
>> arch/powerpc/include/asm/book3s/64/hugetlb.h | 13 +++++++++++++
>> arch/powerpc/mm/hugetlbpage.c | 7 +++++--
>> arch/powerpc/platforms/Kconfig.cputype | 1 +
>> mm/hugetlb.c | 4 ++++
>> 4 files changed, 23 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/hugetlb.h b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> index 6666cd366596..86f27cc8ec61 100644
>> --- a/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> +++ b/arch/powerpc/include/asm/book3s/64/hugetlb.h
>> @@ -50,4 +50,17 @@ static inline pte_t arch_make_huge_pte(pte_t entry, struct vm_area_struct *vma,
>> else
>> return entry;
>> }
>> +
>> +#if defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) && \
>> + ((defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || \
>> + defined(CONFIG_CMA))
>> +#define gigantic_page_supported gigantic_page_supported
>
> As I have mentioned in later part of the reply, it does not really
> make sense to have both arch call back as well as generic config
> option checking to decide on whether a feature is enabled or not.
>
>> +static inline bool gigantic_page_supported(void)
>> +{
>> + if (radix_enabled())
>> + return true;
>> + return false;
>> +}
>> +#endif
>> +
>> #endif
>> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
>> index a4f33de4008e..80f6d2ed551a 100644
>> --- a/arch/powerpc/mm/hugetlbpage.c
>> +++ b/arch/powerpc/mm/hugetlbpage.c
>> @@ -763,8 +763,11 @@ static int __init add_huge_page_size(unsigned long long size)
>> * Hash: 16M and 16G
>> */
>> if (radix_enabled()) {
>> - if (mmu_psize != MMU_PAGE_2M)
>> - return -EINVAL;
>> + if (mmu_psize != MMU_PAGE_2M) {
>> + if (cpu_has_feature(CPU_FTR_POWER9_DD1) ||
>> + (mmu_psize != MMU_PAGE_1G))
>> + return -EINVAL;
>> + }
>> } else {
>> if (mmu_psize != MMU_PAGE_16M && mmu_psize != MMU_PAGE_16G)
>> return -EINVAL;
>> diff --git a/arch/powerpc/platforms/Kconfig.cputype b/arch/powerpc/platforms/Kconfig.cputype
>> index ef4c4b8fc547..f4ba4bf0d762 100644
>> --- a/arch/powerpc/platforms/Kconfig.cputype
>> +++ b/arch/powerpc/platforms/Kconfig.cputype
>> @@ -343,6 +343,7 @@ config PPC_STD_MMU_64
>> config PPC_RADIX_MMU
>> bool "Radix MMU Support"
>> depends on PPC_BOOK3S_64
>> + select ARCH_HAS_GIGANTIC_PAGE
>> default y
>> help
>
> As we are already checking for radix_enabled() test inside function
> gigantic_page_supported(), do we still need to conditionally enable
> this on Radix based platforms only ?
>
>
>> Enable support for the Power ISA 3.0 Radix style MMU. Currently this
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 3d0aab9ee80d..2c090189f314 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -1158,7 +1158,11 @@ static int alloc_fresh_gigantic_page(struct hstate *h,
>> return 0;
>> }
>>
>> +#ifndef gigantic_page_supported
>> static inline bool gigantic_page_supported(void) { return true; }
>> +#define gigantic_page_supported gigantic_page_supported
>> +#endif
>
> As seen above, now that arch's decision to support this feature is not
> based solely on ARCH_HAS_GIGANTIC_PAGE config option but also on the
> availability of platform features like radix, is it a good time to have
> an arch call back deciding on gigantic_page_supported() test instead of
> just checking presence of config options like
>
> #if defined(CONFIG_ARCH_HAS_GIGANTIC_PAGE) && \
> ((defined(CONFIG_MEMORY_ISOLATION) && defined(CONFIG_COMPACTION)) || \
> defined(CONFIG_CMA))
>
> We should not have both as proposed. I mean CONFIG_ARCH_HAS_GIGANTIC_PAGE
> should not be enabled unless we have MEMORY_ISOLATION && COMPACTION && CMA
> and once enabled we should have arch_gigantic_page_supported() deciding for
> gigantic_page_supported().
I will update the patch. I guess I can also fixup other arch that enable
GIGANTIC_PAGE accordingly.
-aneesh
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