arch/tile/mm/highmem.c - kernel/bruno - Git at Google

 /*
  * 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);
 }
	/*
	* 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);
	}