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    SubjectRe: [RFC v2 02/12] powerpc: Free up four 64K PTE bits in 64K backed hpte pages.
    Date
    Ram Pai <linuxram@us.ibm.com> writes:

    ....

    > diff --git a/arch/powerpc/mm/hugetlbpage-hash64.c b/arch/powerpc/mm/hugetlbpage-hash64.c
    > index a84bb44..239ca86 100644
    > --- a/arch/powerpc/mm/hugetlbpage-hash64.c
    > +++ b/arch/powerpc/mm/hugetlbpage-hash64.c
    > @@ -22,6 +22,7 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
    > pte_t *ptep, unsigned long trap, unsigned long flags,
    > int ssize, unsigned int shift, unsigned int mmu_psize)
    > {
    > + real_pte_t rpte;
    > unsigned long vpn;
    > unsigned long old_pte, new_pte;
    > unsigned long rflags, pa, sz;
    > @@ -61,6 +62,7 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
    > } while(!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
    >
    > rflags = htab_convert_pte_flags(new_pte);
    > + rpte = __real_pte(__pte(old_pte), ptep);
    >
    > sz = ((1UL) << shift);
    > if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
    > @@ -71,15 +73,10 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
    > /* Check if pte already has an hpte (case 2) */
    > if (unlikely(old_pte & H_PAGE_HASHPTE)) {
    > /* There MIGHT be an HPTE for this pte */
    > - unsigned long hash, slot;
    > + unsigned long gslot;
    >
    > - hash = hpt_hash(vpn, shift, ssize);
    > - if (old_pte & H_PAGE_F_SECOND)
    > - hash = ~hash;
    > - slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
    > - slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
    > -
    > - if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, mmu_psize,
    > + gslot = get_hidx_gslot(vpn, shift, ssize, rpte, 0);
    > + if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, mmu_psize,
    > mmu_psize, ssize, flags) == -1)
    > old_pte &= ~_PAGE_HPTEFLAGS;
    > }
    > @@ -106,8 +103,7 @@ int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
    > return -1;
    > }
    >
    > - new_pte |= (slot << H_PAGE_F_GIX_SHIFT) &
    > - (H_PAGE_F_SECOND | H_PAGE_F_GIX);
    > + new_pte |= set_hidx_slot(ptep, rpte, 0, slot);

    We don't really need rpte here. We are just need to track one entry
    here. May be it becomes simpler if use different helpers for 4k hpte and
    others ?

    -aneesh

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