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>
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@ -63,13 +63,21 @@ static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep)
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return rpte;
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}
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/*
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* shift the hidx representation by one-modulo-0xf; i.e hidx 0 is respresented
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* as 1, 1 as 2,... , and 0xf as 0. This convention lets us represent a
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* invalid hidx 0xf with a 0x0 bit value. PTEs are anyway zero'd when
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* allocated. We dont have to zero them gain; thus save on the initialization.
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*/
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#define HIDX_UNSHIFT_BY_ONE(x) ((x + 0xfUL) & 0xfUL) /* shift backward by one */
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#define HIDX_SHIFT_BY_ONE(x) ((x + 0x1UL) & 0xfUL) /* shift forward by one */
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#define HIDX_BITS(x, index) (x << (index << 2))
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#define BITS_TO_HIDX(x, index) ((x >> (index << 2)) & 0xfUL)
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#define INVALID_RPTE_HIDX ~(0x0UL)
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#define INVALID_RPTE_HIDX 0x0UL
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static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
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{
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return BITS_TO_HIDX(rpte.hidx, index);
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return HIDX_UNSHIFT_BY_ONE(BITS_TO_HIDX(rpte.hidx, index));
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}
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/*
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@ -82,7 +90,7 @@ static inline unsigned long pte_set_hidx(pte_t *ptep, real_pte_t rpte,
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unsigned long *hidxp = (unsigned long *)(ptep + PTRS_PER_PTE);
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rpte.hidx &= ~HIDX_BITS(0xfUL, subpg_index);
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*hidxp = rpte.hidx | HIDX_BITS(hidx, subpg_index);
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*hidxp = rpte.hidx | HIDX_BITS(HIDX_SHIFT_BY_ONE(hidx), subpg_index);
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/*
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* Anyone reading PTE must ensure hidx bits are read after reading the
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