diff options
Diffstat (limited to 'include/asm-ppc64/mmu_context.h')
| -rw-r--r-- | include/asm-ppc64/mmu_context.h | 82 |
1 files changed, 0 insertions, 82 deletions
diff --git a/include/asm-ppc64/mmu_context.h b/include/asm-ppc64/mmu_context.h index c2e8e04..77a7434 100644 --- a/include/asm-ppc64/mmu_context.h +++ b/include/asm-ppc64/mmu_context.h @@ -84,86 +84,4 @@ static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next) local_irq_restore(flags); } -/* VSID allocation - * =============== - * - * We first generate a 36-bit "proto-VSID". For kernel addresses this - * is equal to the ESID, for user addresses it is: - * (context << 15) | (esid & 0x7fff) - * - * The two forms are distinguishable because the top bit is 0 for user - * addresses, whereas the top two bits are 1 for kernel addresses. - * Proto-VSIDs with the top two bits equal to 0b10 are reserved for - * now. - * - * The proto-VSIDs are then scrambled into real VSIDs with the - * multiplicative hash: - * - * VSID = (proto-VSID * VSID_MULTIPLIER) % VSID_MODULUS - * where VSID_MULTIPLIER = 268435399 = 0xFFFFFC7 - * VSID_MODULUS = 2^36-1 = 0xFFFFFFFFF - * - * This scramble is only well defined for proto-VSIDs below - * 0xFFFFFFFFF, so both proto-VSID and actual VSID 0xFFFFFFFFF are - * reserved. VSID_MULTIPLIER is prime, so in particular it is - * co-prime to VSID_MODULUS, making this a 1:1 scrambling function. - * Because the modulus is 2^n-1 we can compute it efficiently without - * a divide or extra multiply (see below). - * - * This scheme has several advantages over older methods: - * - * - We have VSIDs allocated for every kernel address - * (i.e. everything above 0xC000000000000000), except the very top - * segment, which simplifies several things. - * - * - We allow for 15 significant bits of ESID and 20 bits of - * context for user addresses. i.e. 8T (43 bits) of address space for - * up to 1M contexts (although the page table structure and context - * allocation will need changes to take advantage of this). - * - * - The scramble function gives robust scattering in the hash - * table (at least based on some initial results). The previous - * method was more susceptible to pathological cases giving excessive - * hash collisions. - */ - -/* - * WARNING - If you change these you must make sure the asm - * implementations in slb_allocate(), do_stab_bolted and mmu.h - * (ASM_VSID_SCRAMBLE macro) are changed accordingly. - * - * You'll also need to change the precomputed VSID values in head.S - * which are used by the iSeries firmware. - */ - -static inline unsigned long vsid_scramble(unsigned long protovsid) -{ -#if 0 - /* The code below is equivalent to this function for arguments - * < 2^VSID_BITS, which is all this should ever be called - * with. However gcc is not clever enough to compute the - * modulus (2^n-1) without a second multiply. */ - return ((protovsid * VSID_MULTIPLIER) % VSID_MODULUS); -#else /* 1 */ - unsigned long x; - - x = protovsid * VSID_MULTIPLIER; - x = (x >> VSID_BITS) + (x & VSID_MODULUS); - return (x + ((x+1) >> VSID_BITS)) & VSID_MODULUS; -#endif /* 1 */ -} - -/* This is only valid for addresses >= KERNELBASE */ -static inline unsigned long get_kernel_vsid(unsigned long ea) -{ - return vsid_scramble(ea >> SID_SHIFT); -} - -/* This is only valid for user addresses (which are below 2^41) */ -static inline unsigned long get_vsid(unsigned long context, unsigned long ea) -{ - return vsid_scramble((context << USER_ESID_BITS) - | (ea >> SID_SHIFT)); -} - #endif /* __PPC64_MMU_CONTEXT_H */ |