diff options
Diffstat (limited to 'arch/powerpc')
| -rw-r--r-- | arch/powerpc/mm/mmu_context_nohash.c | 84 |
1 files changed, 39 insertions, 45 deletions
diff --git a/arch/powerpc/mm/mmu_context_nohash.c b/arch/powerpc/mm/mmu_context_nohash.c index 3fbe36266838..3cc59697d253 100644 --- a/arch/powerpc/mm/mmu_context_nohash.c +++ b/arch/powerpc/mm/mmu_context_nohash.c @@ -54,9 +54,34 @@ #include "mmu_decl.h" +/* + * The MPC8xx has only 16 contexts. We rotate through them on each task switch. + * A better way would be to keep track of tasks that own contexts, and implement + * an LRU usage. That way very active tasks don't always have to pay the TLB + * reload overhead. The kernel pages are mapped shared, so the kernel can run on + * behalf of any task that makes a kernel entry. Shared does not mean they are + * not protected, just that the ASID comparison is not performed. -- Dan + * + * The IBM4xx has 256 contexts, so we can just rotate through these as a way of + * "switching" contexts. If the TID of the TLB is zero, the PID/TID comparison + * is disabled, so we can use a TID of zero to represent all kernel pages as + * shared among all contexts. -- Dan + * + * The IBM 47x core supports 16-bit PIDs, thus 65535 contexts. We should + * normally never have to steal though the facility is present if needed. + * -- BenH + */ #define FIRST_CONTEXT 1 +#ifdef DEBUG_CLAMP_LAST_CONTEXT +#define LAST_CONTEXT DEBUG_CLAMP_LAST_CONTEXT +#elif defined(CONFIG_PPC_8xx) +#define LAST_CONTEXT 16 +#elif defined(CONFIG_PPC_47x) +#define LAST_CONTEXT 65535 +#else +#define LAST_CONTEXT 255 +#endif -static unsigned int last_context; static unsigned int next_context, nr_free_contexts; static unsigned long *context_map; static unsigned long *stale_map[NR_CPUS]; @@ -64,7 +89,7 @@ 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)) + (sizeof(unsigned long) * (LAST_CONTEXT / BITS_PER_LONG + 1)) /* Steal a context from a task that has one at the moment. @@ -88,7 +113,7 @@ static unsigned int steal_context_smp(unsigned int id) struct mm_struct *mm; unsigned int cpu, max, i; - max = last_context - FIRST_CONTEXT; + max = LAST_CONTEXT - FIRST_CONTEXT; /* Attempt to free next_context first and then loop until we manage */ while (max--) { @@ -100,7 +125,7 @@ static unsigned int steal_context_smp(unsigned int id) */ if (mm->context.active) { id++; - if (id > last_context) + if (id > LAST_CONTEXT) id = FIRST_CONTEXT; continue; } @@ -143,7 +168,7 @@ static unsigned int steal_all_contexts(void) int cpu = smp_processor_id(); unsigned int id; - for (id = FIRST_CONTEXT; id <= last_context; id++) { + for (id = FIRST_CONTEXT; id <= LAST_CONTEXT; id++) { /* Pick up the victim mm */ mm = context_mm[id]; @@ -164,7 +189,7 @@ static unsigned int steal_all_contexts(void) /* Flush the TLB for all contexts (not to be used on SMP) */ _tlbil_all(); - nr_free_contexts = last_context - FIRST_CONTEXT; + nr_free_contexts = LAST_CONTEXT - FIRST_CONTEXT; return FIRST_CONTEXT; } @@ -202,7 +227,7 @@ static void context_check_map(void) unsigned int id, nrf, nact; nrf = nact = 0; - for (id = FIRST_CONTEXT; id <= last_context; id++) { + for (id = FIRST_CONTEXT; id <= LAST_CONTEXT; id++) { int used = test_bit(id, context_map); if (!used) nrf++; @@ -264,7 +289,7 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, /* We really don't have a context, let's try to acquire one */ id = next_context; - if (id > last_context) + if (id > LAST_CONTEXT) id = FIRST_CONTEXT; map = context_map; @@ -288,8 +313,8 @@ void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, /* 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 = find_next_zero_bit(map, LAST_CONTEXT+1, id); + if (id > LAST_CONTEXT) id = FIRST_CONTEXT; } stolen: @@ -419,41 +444,10 @@ void __init mmu_context_init(void) init_mm.context.active = NR_CPUS; /* - * The MPC8xx has only 16 contexts. We rotate through them on each - * task switch. A better way would be to keep track of tasks that - * own contexts, and implement an LRU usage. That way very active - * tasks don't always have to pay the TLB reload overhead. The - * kernel pages are mapped shared, so the kernel can run on behalf - * of any task that makes a kernel entry. Shared does not mean they - * are not protected, just that the ASID comparison is not performed. - * -- Dan - * - * The IBM4xx has 256 contexts, so we can just rotate through these - * as a way of "switching" contexts. If the TID of the TLB is zero, - * the PID/TID comparison is disabled, so we can use a TID of zero - * to represent all kernel pages as shared among all contexts. - * -- Dan - * - * The IBM 47x core supports 16-bit PIDs, thus 65535 contexts. We - * should normally never have to steal though the facility is - * present if needed. - * -- BenH - */ - if (mmu_has_feature(MMU_FTR_TYPE_8xx)) - last_context = 16; - else if (mmu_has_feature(MMU_FTR_TYPE_47x)) - last_context = 65535; - else - last_context = 255; - -#ifdef DEBUG_CLAMP_LAST_CONTEXT - last_context = DEBUG_CLAMP_LAST_CONTEXT; -#endif - /* * Allocate the maps used by context management */ context_map = memblock_virt_alloc(CTX_MAP_SIZE, 0); - context_mm = memblock_virt_alloc(sizeof(void *) * (last_context + 1), 0); + context_mm = memblock_virt_alloc(sizeof(void *) * (LAST_CONTEXT + 1), 0); #ifndef CONFIG_SMP stale_map[0] = memblock_virt_alloc(CTX_MAP_SIZE, 0); #else @@ -466,8 +460,8 @@ void __init mmu_context_init(void) printk(KERN_INFO "MMU: Allocated %zu bytes of context maps for %d contexts\n", - 2 * CTX_MAP_SIZE + (sizeof(void *) * (last_context + 1)), - last_context - FIRST_CONTEXT + 1); + 2 * CTX_MAP_SIZE + (sizeof(void *) * (LAST_CONTEXT + 1)), + LAST_CONTEXT - FIRST_CONTEXT + 1); /* * Some processors have too few contexts to reserve one for @@ -477,6 +471,6 @@ void __init mmu_context_init(void) */ context_map[0] = (1 << FIRST_CONTEXT) - 1; next_context = FIRST_CONTEXT; - nr_free_contexts = last_context - FIRST_CONTEXT + 1; + nr_free_contexts = LAST_CONTEXT - FIRST_CONTEXT + 1; } |