mmu_context_nohash.rar_Table

/* * This file contains the routines for handling the MMU on those * PowerPC implementations where the MMU is not using the hash * table, such as 8xx, 4xx, BookE's etc... * * Copyright 2008 Ben Herrenschmidt <benh@kernel.crashing.org> * IBM Corp. * * Derived from previous arch/powerpc/mm/mmu_context.c * and arch/powerpc/include/asm/mmu_context.h * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * TODO: * * - The global context lock will not scale very well * - The maps should be dynamically allocated to allow for processors * that support more PID bits at runtime * - Implement flush_tlb_mm() by making the context stale and picking * a new one * - More aggressively clear stale map bits and maybe find some way to * also clear mm->cpu_vm_mask bits when processes are migrated */ //#define DEBUG_MAP_CONSISTENCY //#define DEBUG_CLAMP_LAST_CONTEXT 31 //#define DEBUG_HARDER /* We don't use DEBUG because it tends to be compiled in always nowadays * and this would generate way too much output */ #ifdef DEBUG_HARDER #define pr_hard(args...) printk(KERN_DEBUG args) #define pr_hardcont(args...) printk(KERN_CONT args) #else #define pr_hard(args...) do { } while(0) #define pr_hardcont(args...) do { } while(0) #endif #include <linux/kernel.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/spinlock.h> #include <linux/bootmem.h> #include <linux/notifier.h> #include <linux/cpu.h> #include <linux/slab.h> #include <asm/mmu_context.h> #include <asm/tlbflush.h> static unsigned int first_context, last_context; static unsigned int next_context, nr_free_contexts; static unsigned long *context_map; static unsigned long *stale_map[NR_CPUS]; static struct mm_struct **context_mm; static DEFINE_RAW_SPINLOCK(context_lock); #define CTX_MAP_SIZE \ (sizeof(unsigned long) * (last_context / BITS_PER_LONG + 1)) /* Steal a context from a task that has one at the moment. * * This is used when we are running out of available PID numbers * on the processors. * * This isn't an LRU system, it just frees up each context in * turn (sort-of pseudo-random replacement :). This would be the * place to implement an LRU scheme if anyone was motivated to do it. * -- paulus * * For context stealing, we use a slightly different approach for * SMP and UP. Basically, the UP one is simpler and doesn't use * the stale map as we can just flush the local CPU * -- benh */ #ifdef CONFIG_SMP static unsigned int steal_context_smp(unsigned int id) { struct mm_struct *mm; unsigned int cpu, max, i; max = last_context - first_context; /* Attempt to free next_context first and then loop until we manage */ while (max--) { /* Pick up the victim mm */ mm = context_mm[id]; /* We have a candidate victim, check if it's active, on SMP * we cannot steal active contexts */ if (mm->context.active) { id++; if (id > last_context) id = first_context; continue; } pr_hardcont(" | steal %d from 0x%p", id, mm); /* Mark this mm has having no context anymore */ mm->context.id = MMU_NO_CONTEXT; /* Mark it stale on all CPUs that used this mm. For threaded * implementations, we set it on all threads on each core * represented in the mask. A future implementation will use * a core map instead but this will do for now. */ for_each_cpu(cpu, mm_cpumask(mm)) { for (i = cpu_first_thread_sibling(cpu); i <= cpu_last_thread_sibling(cpu); i++) { if (stale_map[i]) __set_bit(id, stale_map[i]); } cpu = i - 1; } return id; } /* This will happen if you have more CPUs than available contexts, * all we can do here is wait a bit and try again */ raw_spin_unlock(&context_lock); cpu_relax(); raw_spin_lock(&context_lock); /* This will cause the caller to try again */ return MMU_NO_CONTEXT; } #endif /* CONFIG_SMP */ /* Note that this will also be called on SMP if all other CPUs are * offlined, which means that it may be called for cpu != 0. For * this to work, we somewhat assume that CPUs that are onlined * come up with a fully clean TLB (or are cleaned when offlined) */ static unsigned int steal_context_up(unsigned int id) { struct mm_struct *mm; int cpu = smp_processor_id(); /* Pick up the victim mm */ mm = context_mm[id]; pr_hardcont(" | steal %d from 0x%p", id, mm); /* Flush the TLB for that context */ local_flush_tlb_mm(mm); /* Mark this mm has having no context anymore */ mm->context.id = MMU_NO_CONTEXT; /* XXX This clear should ultimately be part of local_flush_tlb_mm */ __clear_bit(id, stale_map[cpu]); return id; } #ifdef DEBUG_MAP_CONSISTENCY static void context_check_map(void) { unsigned int id, nrf, nact; nrf = nact = 0; for (id = first_context; id <= last_context; id++) { int used = test_bit(id, context_map); if (!used) nrf++; if (used != (context_mm[id] != NULL)) pr_err("MMU: Context %d is %s and MM is %p !\n", id, used ? "used" : "free", context_mm[id]); if (context_mm[id] != NULL) nact += context_mm[id]->context.active; } if (nrf != nr_free_contexts) { pr_err("MMU: Free context count out of sync ! (%d vs %d)\n", nr_free_contexts, nrf); nr_free_contexts = nrf; } if (nact > num_online_cpus()) pr_err("MMU: More active contexts than CPUs ! (%d vs %d)\n", nact, num_online_cpus()); if (first_context > 0 && !test_bit(0, context_map)) pr_err("MMU: Context 0 has been freed !!!\n"); } #else static void context_check_map(void) { } #endif void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next) { unsigned int i, id, cpu = smp_processor_id(); unsigned long *map; /* No lockless fast path .. yet */ raw_spin_lock(&context_lock); pr_hard("[%d] activating context for mm @%p, active=%d, id=%d", cpu, next, next->context.active, next->context.id); #ifdef CONFIG_SMP /* Mark us active and the previous one not anymore */ next->context.active++; if (prev) { pr_hardcont(" (old=0x%p a=%d)", prev, prev->context.active); WARN_ON(prev->context.active < 1); prev->context.active--; } again: #endif /* CONFIG_SMP */ /* If we already have a valid assigned context, skip all that */ id = next->context.id; if (likely(id != MMU_NO_CONTEXT)) { #ifdef DEBUG_MAP_CONSISTENCY if (context_mm[id] != next) pr_err("MMU: mm 0x%p has id %d but context_mm[%d] says 0x%p\n", next, id, id, context_mm[id]); #endif goto ctxt_ok; } /* We really don't have a context, let's try to acquire one */ id = next_context; if (id > last_context) id = first_context; map = context_map; /* No more free contexts, let's try to steal one */ if (nr_free_contexts == 0) { #ifdef CONFIG_SMP if (num_online_cpus() > 1) { id = steal_context_smp(id); if (id == MMU_NO_CONTEXT) goto again; goto stolen; } #endif /* CONFIG_SMP */ id = steal_context_up(id); goto stolen; } nr_free_contexts--; /* We know there's at least one free context, try to find it */ while (__test_and_set_bit(id, map)) { id = find_next_zero_bit(map, last_context+1, id); if (id > last_context) id = first_context; } stolen: next_context = id + 1; context_mm[id] = next; next->context.id = id; pr_hardcont(" | new id=%d,nrf=%d", id, nr_free_contexts); context_check_map(); ctxt_ok: /* If that context got marked stale on this CPU, then flush the * local TLB for it and unmark it before we use it */ if (test_bit(id, stale_map[cpu])) { pr_hardcont(" | stale flush %d [%d..%d]", id, cpu_first_thread_sibling(cpu), cpu_last_thread_sibling(cpu)); local_flush_tlb_mm(next); /* XXX This clear should ultimately be part of local_flush_tlb_mm */ for (i = cpu_first_thread_sibling(cpu); i <= cpu_last_thread_sibling(cpu); i++) { if (stale_m