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Subject[RFC v6 03/62] powerpc: introduce pte_set_hash_slot() helper
Date
Introduce pte_set_hash_slot().It  sets the (H_PAGE_F_SECOND|H_PAGE_F_GIX)
bits at the appropriate location in the PTE of 4K PTE. For
64K PTE, it sets the bits in the second part of the PTE. Though
the implementation for the former just needs the slot parameter, it does
take some additional parameters to keep the prototype consistent.

This function will be handy as we work towards re-arranging the
bits in the later patches.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
---
arch/powerpc/include/asm/book3s/64/hash-4k.h | 15 +++++++++++++++
arch/powerpc/include/asm/book3s/64/hash-64k.h | 25 +++++++++++++++++++++++++
2 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/hash-4k.h b/arch/powerpc/include/asm/book3s/64/hash-4k.h
index d2cf949..dc153c6 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-4k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h
@@ -53,6 +53,21 @@ static inline int hash__hugepd_ok(hugepd_t hpd)
}
#endif

+/*
+ * 4k pte format is different from 64k pte format. Saving the
+ * hash_slot is just a matter of returning the pte bits that need to
+ * be modified. On 64k pte, things are a little more involved and
+ * hence needs many more parameters to accomplish the same.
+ * However we want to abstract this out from the caller by keeping
+ * the prototype consistent across the two formats.
+ */
+static inline unsigned long pte_set_hash_slot(pte_t *ptep, real_pte_t rpte,
+ unsigned int subpg_index, unsigned long slot)
+{
+ return (slot << H_PAGE_F_GIX_SHIFT) &
+ (H_PAGE_F_SECOND | H_PAGE_F_GIX);
+}
+
#ifdef CONFIG_TRANSPARENT_HUGEPAGE

static inline char *get_hpte_slot_array(pmd_t *pmdp)
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index c281f18..89ef5a9 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -67,6 +67,31 @@ static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
return ((rpte.hidx >> (index<<2)) & 0xfUL);
}

+/*
+ * Commit the hash slot and return pte bits that needs to be modified.
+ * The caller is expected to modify the pte bits accordingly and
+ * commit the pte to memory.
+ */
+static inline unsigned long pte_set_hash_slot(pte_t *ptep, real_pte_t rpte,
+ unsigned int subpg_index, unsigned long slot)
+{
+ unsigned long *hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
+
+ rpte.hidx &= ~(0xfUL << (subpg_index << 2));
+ *hidxp = rpte.hidx | (slot << (subpg_index << 2));
+ /*
+ * Commit the hidx bits to memory before returning.
+ * Anyone reading pte must ensure hidx bits are
+ * read only after reading the pte by using the
+ * read-side barrier smp_rmb(). __real_pte() can
+ * help ensure that.
+ */
+ smp_wmb();
+
+ /* no pte bits to be modified, return 0x0UL */
+ return 0x0UL;
+}
+
#define __rpte_to_pte(r) ((r).pte)
extern bool __rpte_sub_valid(real_pte_t rpte, unsigned long index);
/*
--
1.7.1
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