On 04/11/2016 07:21 PM, Balbir Singh wrote:
>
>
> On 07/04/16 15:37, Anshuman Khandual wrote:
>> Currently the function 'huge_pte_alloc' has got two versions, one for the
>> BOOK3S server and the other one for the BOOK3E embedded platforms. This
>> change splits only the BOOK3S server version into two parts, one for the
>> ARCH_WANT_GENERAL_HUGETLB config implementation and the other one for
>> everything else. This change is one of the prerequisites towards enabling
>> ARCH_WANT_GENERAL_HUGETLB config option on POWER platform.
>>
>> Signed-off-by: Anshuman Khandual <khand...@linux.vnet.ibm.com>
>> ---
>> arch/powerpc/mm/hugetlbpage.c | 67
>> +++++++++++++++++++++++++++----------------
>> 1 file changed, 43 insertions(+), 24 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
>> index d991b9e..e453918 100644
>> --- a/arch/powerpc/mm/hugetlbpage.c
>> +++ b/arch/powerpc/mm/hugetlbpage.c
>> @@ -59,6 +59,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long
>> addr)
>> return __find_linux_pte_or_hugepte(mm->pgd, addr, NULL, NULL);
>> }
>>
>> +#ifndef CONFIG_ARCH_WANT_GENERAL_HUGETLB
>> static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
>> unsigned long address, unsigned pdshift, unsigned
>> pshift)
>> {
>> @@ -116,6 +117,7 @@ static int __hugepte_alloc(struct mm_struct *mm,
>> hugepd_t *hpdp,
>> spin_unlock(&mm->page_table_lock);
>> return 0;
>> }
>> +#endif /* !CONFIG_ARCH_WANT_GENERAL_HUGETLB */
>>
>> /*
>> * These macros define how to determine which level of the page table holds
>> @@ -130,6 +132,7 @@ static int __hugepte_alloc(struct mm_struct *mm,
>> hugepd_t *hpdp,
>> #endif
>>
>> #ifdef CONFIG_PPC_BOOK3S_64
>> +#ifndef CONFIG_ARCH_WANT_GENERAL_HUGETLB
>> /*
>> * At this point we do the placement change only for BOOK3S 64. This would
>> * possibly work on other subarchs.
>> @@ -145,32 +148,23 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned
>> long addr, unsigned long sz
>>
>> addr &= ~(sz-1);
>> pg = pgd_offset(mm, addr);
>> -
>> - if (pshift == PGDIR_SHIFT)
>> - /* 16GB huge page */
>> - return (pte_t *) pg;
>> - else if (pshift > PUD_SHIFT)
>> - /*
>> - * We need to use hugepd table
>> - */
>> + if (pshift > PUD_SHIFT) {
>> hpdp = (hugepd_t *)pg;
>> - else {
>> - pdshift = PUD_SHIFT;
>> - pu = pud_alloc(mm, pg, addr);
>> - if (pshift == PUD_SHIFT)
>> - return (pte_t *)pu;
>> - else if (pshift > PMD_SHIFT)
>> - hpdp = (hugepd_t *)pu;
>> - else {
>> - pdshift = PMD_SHIFT;
>> - pm = pmd_alloc(mm, pu, addr);
>> - if (pshift == PMD_SHIFT)
>> - /* 16MB hugepage */
>> - return (pte_t *)pm;
>> - else
>> - hpdp = (hugepd_t *)pm;
>> - }
>> + goto hugepd_search;
>> }
>> +
>> + pdshift = PUD_SHIFT;
>> + pu = pud_alloc(mm, pg, addr);
>> + if (pshift > PMD_SHIFT) {
>> + hpdp = (hugepd_t *)pu;
>> + goto hugepd_search;
>> + }
>> +
>> + pdshift = PMD_SHIFT;
>> + pm = pmd_alloc(mm, pu, addr);
>> + hpdp = (hugepd_t *)pm;
>> +
>> +hugepd_search:
>> if (!hpdp)
>> return NULL;
>>
>> @@ -182,6 +176,31 @@ pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned
>> long addr, unsigned long sz
>> return hugepte_offset(*hpdp, addr, pdshift);
>> }
>>
>> +#else /* CONFIG_ARCH_WANT_GENERAL_HUGETLB */
>> +pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned
>> long sz)
>
> This is confusing, aren't we using the one from mm/hugetlb.c?
We are using huge_pte_alloc() from mm/hugetlb.c only when we have
CONFIG_ARCH_WANT_GENERAL_HUGETLB enabled. For every thing else we
use the definition here for BOOK3S platforms.
>
>> +{
>> + pgd_t *pg;
>> + pud_t *pu;
>> + pmd_t *pm;
>> + unsigned pshift = __ffs(sz);
>> +
>> + addr &= ~(sz-1);
>
> Am I reading this right? Shouldn't this be addr &= ~(1 << pshift - 1)
Both are same. __ffs() computes the __ilog2 of the size and arrives at
the page shift. Here we use the size directly instead.
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