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Diffstat (limited to 'arch/tile/mm/highmem.c')
| -rw-r--r-- | arch/tile/mm/highmem.c | 290 |
1 files changed, 290 insertions, 0 deletions
diff --git a/arch/tile/mm/highmem.c b/arch/tile/mm/highmem.c new file mode 100644 index 00000000..ef8e5a62 --- /dev/null +++ b/arch/tile/mm/highmem.c @@ -0,0 +1,290 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * 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, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + */ + +#include <linux/highmem.h> +#include <linux/module.h> +#include <linux/pagemap.h> +#include <asm/homecache.h> + +#define kmap_get_pte(vaddr) \ + pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)),\ + (vaddr)), (vaddr)) + + +void *kmap(struct page *page) +{ + void *kva; + unsigned long flags; + pte_t *ptep; + + might_sleep(); + if (!PageHighMem(page)) + return page_address(page); + kva = kmap_high(page); + + /* + * Rewrite the PTE under the lock. This ensures that the page + * is not currently migrating. + */ + ptep = kmap_get_pte((unsigned long)kva); + flags = homecache_kpte_lock(); + set_pte_at(&init_mm, kva, ptep, mk_pte(page, page_to_kpgprot(page))); + homecache_kpte_unlock(flags); + + return kva; +} +EXPORT_SYMBOL(kmap); + +void kunmap(struct page *page) +{ + if (in_interrupt()) + BUG(); + if (!PageHighMem(page)) + return; + kunmap_high(page); +} +EXPORT_SYMBOL(kunmap); + +/* + * Describe a single atomic mapping of a page on a given cpu at a + * given address, and allow it to be linked into a list. + */ +struct atomic_mapped_page { + struct list_head list; + struct page *page; + int cpu; + unsigned long va; +}; + +static spinlock_t amp_lock = __SPIN_LOCK_UNLOCKED(&_lock); +static struct list_head amp_list = LIST_HEAD_INIT(amp_list); + +/* + * Combining this structure with a per-cpu declaration lets us give + * each cpu an atomic_mapped_page structure per type. + */ +struct kmap_amps { + struct atomic_mapped_page per_type[KM_TYPE_NR]; +}; +static DEFINE_PER_CPU(struct kmap_amps, amps); + +/* + * Add a page and va, on this cpu, to the list of kmap_atomic pages, + * and write the new pte to memory. Writing the new PTE under the + * lock guarantees that it is either on the list before migration starts + * (if we won the race), or set_pte() sets the migrating bit in the PTE + * (if we lost the race). And doing it under the lock guarantees + * that when kmap_atomic_fix_one_pte() comes along, it finds a valid + * PTE in memory, iff the mapping is still on the amp_list. + * + * Finally, doing it under the lock lets us safely examine the page + * to see if it is immutable or not, for the generic kmap_atomic() case. + * If we examine it earlier we are exposed to a race where it looks + * writable earlier, but becomes immutable before we write the PTE. + */ +static void kmap_atomic_register(struct page *page, enum km_type type, + unsigned long va, pte_t *ptep, pte_t pteval) +{ + unsigned long flags; + struct atomic_mapped_page *amp; + + flags = homecache_kpte_lock(); + spin_lock(&_lock); + + /* With interrupts disabled, now fill in the per-cpu info. */ + amp = &__get_cpu_var(amps).per_type[type]; + amp->page = page; + amp->cpu = smp_processor_id(); + amp->va = va; + + /* For generic kmap_atomic(), choose the PTE writability now. */ + if (!pte_read(pteval)) + pteval = mk_pte(page, page_to_kpgprot(page)); + + list_add(&->list, &_list); + set_pte(ptep, pteval); + arch_flush_lazy_mmu_mode(); + + spin_unlock(&_lock); + homecache_kpte_unlock(flags); +} + +/* + * Remove a page and va, on this cpu, from the list of kmap_atomic pages. + * Linear-time search, but we count on the lists being short. + * We don't need to adjust the PTE under the lock (as opposed to the + * kmap_atomic_register() case), since we're just unconditionally + * zeroing the PTE after it's off the list. + */ +static void kmap_atomic_unregister(struct page *page, unsigned long va) +{ + unsigned long flags; + struct atomic_mapped_page *amp; + int cpu = smp_processor_id(); + spin_lock_irqsave(&_lock, flags); + list_for_each_entry(amp, &_list, list) { + if (amp->page == page && amp->cpu == cpu && amp->va == va) + break; + } + BUG_ON(&->list == &_list); + list_del(&->list); + spin_unlock_irqrestore(&_lock, flags); +} + +/* Helper routine for kmap_atomic_fix_kpte(), below. */ +static void kmap_atomic_fix_one_kpte(struct atomic_mapped_page *amp, + int finished) +{ + pte_t *ptep = kmap_get_pte(amp->va); + if (!finished) { + set_pte(ptep, pte_mkmigrate(*ptep)); + flush_remote(0, 0, NULL, amp->va, PAGE_SIZE, PAGE_SIZE, + cpumask_of(amp->cpu), NULL, 0); + } else { + /* + * Rewrite a default kernel PTE for this page. + * We rely on the fact that set_pte() writes the + * present+migrating bits last. + */ + pte_t pte = mk_pte(amp->page, page_to_kpgprot(amp->page)); + set_pte(ptep, pte); + } +} + +/* + * This routine is a helper function for homecache_fix_kpte(); see + * its comments for more information on the "finished" argument here. + * + * Note that we hold the lock while doing the remote flushes, which + * will stall any unrelated cpus trying to do kmap_atomic operations. + * We could just update the PTEs under the lock, and save away copies + * of the structs (or just the va+cpu), then flush them after we + * release the lock, but it seems easier just to do it all under the lock. + */ +void kmap_atomic_fix_kpte(struct page *page, int finished) +{ + struct atomic_mapped_page *amp; + unsigned long flags; + spin_lock_irqsave(&_lock, flags); + list_for_each_entry(amp, &_list, list) { + if (amp->page == page) + kmap_atomic_fix_one_kpte(amp, finished); + } + spin_unlock_irqrestore(&_lock, flags); +} + +/* + * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap + * because the kmap code must perform a global TLB invalidation when + * the kmap pool wraps. + * + * Note that they may be slower than on x86 (etc.) because unlike on + * those platforms, we do have to take a global lock to map and unmap + * pages on Tile (see above). + * + * When holding an atomic kmap is is not legal to sleep, so atomic + * kmaps are appropriate for short, tight code paths only. + */ +void *kmap_atomic_prot(struct page *page, pgprot_t prot) +{ + unsigned long vaddr; + int idx, type; + pte_t *pte; + + /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */ + pagefault_disable(); + + /* Avoid icache flushes by disallowing atomic executable mappings. */ + BUG_ON(pte_exec(prot)); + + if (!PageHighMem(page)) + return page_address(page); + + type = kmap_atomic_idx_push(); + idx = type + KM_TYPE_NR*smp_processor_id(); + vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); + pte = kmap_get_pte(vaddr); + BUG_ON(!pte_none(*pte)); + + /* Register that this page is mapped atomically on this cpu. */ + kmap_atomic_register(page, type, vaddr, pte, mk_pte(page, prot)); + + return (void *)vaddr; +} +EXPORT_SYMBOL(kmap_atomic_prot); + +void *kmap_atomic(struct page *page) +{ + /* PAGE_NONE is a magic value that tells us to check immutability. */ + return kmap_atomic_prot(page, PAGE_NONE); +} +EXPORT_SYMBOL(kmap_atomic); + +void __kunmap_atomic(void *kvaddr) +{ + unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK; + + if (vaddr >= __fix_to_virt(FIX_KMAP_END) && + vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) { + pte_t *pte = kmap_get_pte(vaddr); + pte_t pteval = *pte; + int idx, type; + + type = kmap_atomic_idx(); + idx = type + KM_TYPE_NR*smp_processor_id(); + + /* + * Force other mappings to Oops if they try to access this pte + * without first remapping it. Keeping stale mappings around + * is a bad idea. + */ + BUG_ON(!pte_present(pteval) && !pte_migrating(pteval)); + kmap_atomic_unregister(pte_page(pteval), vaddr); + kpte_clear_flush(pte, vaddr); + kmap_atomic_idx_pop(); + } else { + /* Must be a lowmem page */ + BUG_ON(vaddr < PAGE_OFFSET); + BUG_ON(vaddr >= (unsigned long)high_memory); + } + + arch_flush_lazy_mmu_mode(); + pagefault_enable(); +} +EXPORT_SYMBOL(__kunmap_atomic); + +/* + * This API is supposed to allow us to map memory without a "struct page". + * Currently we don't support this, though this may change in the future. + */ +void *kmap_atomic_pfn(unsigned long pfn) +{ + return kmap_atomic(pfn_to_page(pfn)); +} +void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot) +{ + return kmap_atomic_prot(pfn_to_page(pfn), prot); +} + +struct page *kmap_atomic_to_page(void *ptr) +{ + pte_t *pte; + unsigned long vaddr = (unsigned long)ptr; + + if (vaddr < FIXADDR_START) + return virt_to_page(ptr); + + pte = kmap_get_pte(vaddr); + return pte_page(*pte); +} |