![Linus Torvalds](/assets/img/avatar_default.png)
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
170 lines
5.2 KiB
C
170 lines
5.2 KiB
C
#ifndef __PPC64_MMU_CONTEXT_H
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#define __PPC64_MMU_CONTEXT_H
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#include <linux/config.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <asm/mmu.h>
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#include <asm/cputable.h>
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/*
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* Copyright (C) 2001 PPC 64 Team, IBM Corp
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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/*
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* Every architecture must define this function. It's the fastest
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* way of searching a 140-bit bitmap where the first 100 bits are
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* unlikely to be set. It's guaranteed that at least one of the 140
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* bits is cleared.
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*/
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static inline int sched_find_first_bit(unsigned long *b)
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{
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if (unlikely(b[0]))
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return __ffs(b[0]);
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if (unlikely(b[1]))
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return __ffs(b[1]) + 64;
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return __ffs(b[2]) + 128;
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}
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static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
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{
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}
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#define NO_CONTEXT 0
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#define MAX_CONTEXT (0x100000-1)
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extern int init_new_context(struct task_struct *tsk, struct mm_struct *mm);
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extern void destroy_context(struct mm_struct *mm);
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extern void switch_stab(struct task_struct *tsk, struct mm_struct *mm);
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extern void switch_slb(struct task_struct *tsk, struct mm_struct *mm);
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/*
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* switch_mm is the entry point called from the architecture independent
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* code in kernel/sched.c
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*/
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static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
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struct task_struct *tsk)
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{
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if (!cpu_isset(smp_processor_id(), next->cpu_vm_mask))
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cpu_set(smp_processor_id(), next->cpu_vm_mask);
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/* No need to flush userspace segments if the mm doesnt change */
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if (prev == next)
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return;
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#ifdef CONFIG_ALTIVEC
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if (cpu_has_feature(CPU_FTR_ALTIVEC))
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asm volatile ("dssall");
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#endif /* CONFIG_ALTIVEC */
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if (cpu_has_feature(CPU_FTR_SLB))
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switch_slb(tsk, next);
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else
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switch_stab(tsk, next);
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}
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#define deactivate_mm(tsk,mm) do { } while (0)
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/*
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* After we have set current->mm to a new value, this activates
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* the context for the new mm so we see the new mappings.
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*/
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static inline void activate_mm(struct mm_struct *prev, struct mm_struct *next)
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{
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unsigned long flags;
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local_irq_save(flags);
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switch_mm(prev, next, current);
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local_irq_restore(flags);
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}
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/* VSID allocation
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* ===============
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*
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* We first generate a 36-bit "proto-VSID". For kernel addresses this
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* is equal to the ESID, for user addresses it is:
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* (context << 15) | (esid & 0x7fff)
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*
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* The two forms are distinguishable because the top bit is 0 for user
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* addresses, whereas the top two bits are 1 for kernel addresses.
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* Proto-VSIDs with the top two bits equal to 0b10 are reserved for
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* now.
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*
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* The proto-VSIDs are then scrambled into real VSIDs with the
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* multiplicative hash:
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*
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* VSID = (proto-VSID * VSID_MULTIPLIER) % VSID_MODULUS
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* where VSID_MULTIPLIER = 268435399 = 0xFFFFFC7
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* VSID_MODULUS = 2^36-1 = 0xFFFFFFFFF
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*
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* This scramble is only well defined for proto-VSIDs below
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* 0xFFFFFFFFF, so both proto-VSID and actual VSID 0xFFFFFFFFF are
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* reserved. VSID_MULTIPLIER is prime, so in particular it is
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* co-prime to VSID_MODULUS, making this a 1:1 scrambling function.
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* Because the modulus is 2^n-1 we can compute it efficiently without
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* a divide or extra multiply (see below).
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*
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* This scheme has several advantages over older methods:
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*
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* - We have VSIDs allocated for every kernel address
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* (i.e. everything above 0xC000000000000000), except the very top
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* segment, which simplifies several things.
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*
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* - We allow for 15 significant bits of ESID and 20 bits of
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* context for user addresses. i.e. 8T (43 bits) of address space for
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* up to 1M contexts (although the page table structure and context
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* allocation will need changes to take advantage of this).
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*
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* - The scramble function gives robust scattering in the hash
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* table (at least based on some initial results). The previous
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* method was more susceptible to pathological cases giving excessive
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* hash collisions.
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*/
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/*
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* WARNING - If you change these you must make sure the asm
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* implementations in slb_allocate(), do_stab_bolted and mmu.h
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* (ASM_VSID_SCRAMBLE macro) are changed accordingly.
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*
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* You'll also need to change the precomputed VSID values in head.S
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* which are used by the iSeries firmware.
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*/
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static inline unsigned long vsid_scramble(unsigned long protovsid)
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{
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#if 0
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/* The code below is equivalent to this function for arguments
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* < 2^VSID_BITS, which is all this should ever be called
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* with. However gcc is not clever enough to compute the
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* modulus (2^n-1) without a second multiply. */
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return ((protovsid * VSID_MULTIPLIER) % VSID_MODULUS);
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#else /* 1 */
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unsigned long x;
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x = protovsid * VSID_MULTIPLIER;
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x = (x >> VSID_BITS) + (x & VSID_MODULUS);
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return (x + ((x+1) >> VSID_BITS)) & VSID_MODULUS;
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#endif /* 1 */
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}
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/* This is only valid for addresses >= KERNELBASE */
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static inline unsigned long get_kernel_vsid(unsigned long ea)
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{
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return vsid_scramble(ea >> SID_SHIFT);
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}
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/* This is only valid for user addresses (which are below 2^41) */
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static inline unsigned long get_vsid(unsigned long context, unsigned long ea)
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{
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return vsid_scramble((context << USER_ESID_BITS)
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| (ea >> SID_SHIFT));
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}
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#endif /* __PPC64_MMU_CONTEXT_H */
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