Initial import

1 files changed, 288 insertions, 0 deletions

diff --git a/arch/tile/mm/highmem.c b/arch/tile/mm/highmem.c
new file mode 100644
index 000000000..6aa2f2625
--- /dev/null
+++ b/arch/tile/mm/highmem.c
@@ -0,0 +1,288 @@
+/*
+ * 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(&amp_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, int type,
+				 unsigned long va, pte_t *ptep, pte_t pteval)
+{
+	unsigned long flags;
+	struct atomic_mapped_page *amp;
+
+	flags = homecache_kpte_lock();
+	spin_lock(&amp_lock);
+
+	/* With interrupts disabled, now fill in the per-cpu info. */
+	amp = this_cpu_ptr(&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(&amp->list, &amp_list);
+	set_pte(ptep, pteval);
+
+	spin_unlock(&amp_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(&amp_lock, flags);
+	list_for_each_entry(amp, &amp_list, list) {
+		if (amp->page == page && amp->cpu == cpu && amp->va == va)
+			break;
+	}
+	BUG_ON(&amp->list == &amp_list);
+	list_del(&amp->list);
+	spin_unlock_irqrestore(&amp_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(&amp_lock, flags);
+	list_for_each_entry(amp, &amp_list, list) {
+		if (amp->page == page)
+			kmap_atomic_fix_one_kpte(amp, finished);
+	}
+	spin_unlock_irqrestore(&amp_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);
+	}
+
+	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);
+}