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