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| author | Ram Pai <linuxram@us.ibm.com> | 2017-11-06 00:50:49 -0800 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2017-12-20 18:57:23 +1100 |
| commit | 7b84947cadf18f9a7763f281509db1f24073b4af (patch) | |
| tree | 639e0cf44a56bcbd031714cbec988ec51faa82d1 /arch/powerpc/include/asm/book3s | |
| parent | bf9a95f9a6481bc6ec98ef7b328c14177eeb3492 (diff) | |
| download | linux-7b84947cadf18f9a7763f281509db1f24073b4af.tar.gz linux-7b84947cadf18f9a7763f281509db1f24073b4af.tar.xz | |
powerpc: shifted-by-one hidx value
0xf is considered invalid hidx value. It indicates absence of a backing
HPTE. A PTE is initialized to 0xf either
a) when it is new it is newly allocated to hold 4k-backing-HPTE
or
b) Any time it gets demoted to a 4k-backing-HPTE
This patch shifts the representation by one-modulo-0xf; i.e hidx 0 is
represented as 1, 1 as 2,... , and 0xf as 0. This convention lets us
initialize the secondary-part of the PTE to all zeroes. PTEs are anyway
zero'd when allocated. We do not have to zero them again; thus saving on
the initialization.
Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/include/asm/book3s')
| -rw-r--r-- | arch/powerpc/include/asm/book3s/64/hash-64k.h | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h index 73ed988e6da5..b78d94e5249b 100644 --- a/arch/powerpc/include/asm/book3s/64/hash-64k.h +++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h @@ -63,13 +63,21 @@ static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep) return rpte; } +/* + * shift the hidx representation by one-modulo-0xf; i.e hidx 0 is respresented + * as 1, 1 as 2,... , and 0xf as 0. This convention lets us represent a + * invalid hidx 0xf with a 0x0 bit value. PTEs are anyway zero'd when + * allocated. We dont have to zero them gain; thus save on the initialization. + */ +#define HIDX_UNSHIFT_BY_ONE(x) ((x + 0xfUL) & 0xfUL) /* shift backward by one */ +#define HIDX_SHIFT_BY_ONE(x) ((x + 0x1UL) & 0xfUL) /* shift forward by one */ #define HIDX_BITS(x, index) (x << (index << 2)) #define BITS_TO_HIDX(x, index) ((x >> (index << 2)) & 0xfUL) -#define INVALID_RPTE_HIDX ~(0x0UL) +#define INVALID_RPTE_HIDX 0x0UL static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index) { - return BITS_TO_HIDX(rpte.hidx, index); + return HIDX_UNSHIFT_BY_ONE(BITS_TO_HIDX(rpte.hidx, index)); } /* @@ -82,7 +90,7 @@ static inline unsigned long pte_set_hidx(pte_t *ptep, real_pte_t rpte, unsigned long *hidxp = (unsigned long *)(ptep + PTRS_PER_PTE); rpte.hidx &= ~HIDX_BITS(0xfUL, subpg_index); - *hidxp = rpte.hidx | HIDX_BITS(hidx, subpg_index); + *hidxp = rpte.hidx | HIDX_BITS(HIDX_SHIFT_BY_ONE(hidx), subpg_index); /* * Anyone reading PTE must ensure hidx bits are read after reading the |