[net-next-2.6.git] / arch / tile / mm / highmem.c

/*
 * 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, 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(&amp_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(&amp->list, &amp_list);
	set_pte(ptep, pteval);
	arch_flush_lazy_mmu_mode();

	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);
	}

	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);
}
Commit	Line	Data
867e359b CM	1	/*
	2	* Copyright 2010 Tilera Corporation. All Rights Reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or
	5	* modify it under the terms of the GNU General Public License
	6	* as published by the Free Software Foundation, version 2.
	7	*
	8	* This program is distributed in the hope that it will be useful, but
	9	* WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
	11	* NON INFRINGEMENT. See the GNU General Public License for
	12	* more details.
	13	*/
	14
	15	#include <linux/highmem.h>
	16	#include <linux/module.h>
	17	#include <linux/pagemap.h>
	18	#include <asm/homecache.h>
	19
	20	#define kmap_get_pte(vaddr) \
	21	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)),\
	22	(vaddr)), (vaddr))
	23
	24
	25	void kmap(struct page page)
	26	{
	27	void *kva;
	28	unsigned long flags;
	29	pte_t *ptep;
	30
	31	might_sleep();
	32	if (!PageHighMem(page))
	33	return page_address(page);
	34	kva = kmap_high(page);
	35
	36	/*
	37	* Rewrite the PTE under the lock. This ensures that the page
	38	* is not currently migrating.
	39	*/
	40	ptep = kmap_get_pte((unsigned long)kva);
	41	flags = homecache_kpte_lock();
	42	set_pte_at(&init_mm, kva, ptep, mk_pte(page, page_to_kpgprot(page)));
	43	homecache_kpte_unlock(flags);
	44
	45	return kva;
	46	}
	47	EXPORT_SYMBOL(kmap);
	48
	49	void kunmap(struct page *page)
	50	{
	51	if (in_interrupt())
	52	BUG();
	53	if (!PageHighMem(page))
	54	return;
	55	kunmap_high(page);
	56	}
	57	EXPORT_SYMBOL(kunmap);
	58
867e359b CM	59	/*
	60	* Describe a single atomic mapping of a page on a given cpu at a
	61	* given address, and allow it to be linked into a list.
	62	*/
	63	struct atomic_mapped_page {
	64	struct list_head list;
	65	struct page *page;
	66	int cpu;
	67	unsigned long va;
	68	};
	69
	70	static spinlock_t amp_lock = __SPIN_LOCK_UNLOCKED(&amp_lock);
	71	static struct list_head amp_list = LIST_HEAD_INIT(amp_list);
	72
	73	/*
	74	* Combining this structure with a per-cpu declaration lets us give
	75	* each cpu an atomic_mapped_page structure per type.
	76	*/
	77	struct kmap_amps {
	78	struct atomic_mapped_page per_type[KM_TYPE_NR];
	79	};
0707ad30	80	static DEFINE_PER_CPU(struct kmap_amps, amps);
867e359b CM	81
	82	/*
	83	* Add a page and va, on this cpu, to the list of kmap_atomic pages,
	84	* and write the new pte to memory. Writing the new PTE under the
	85	* lock guarantees that it is either on the list before migration starts
	86	* (if we won the race), or set_pte() sets the migrating bit in the PTE
	87	* (if we lost the race). And doing it under the lock guarantees
	88	* that when kmap_atomic_fix_one_pte() comes along, it finds a valid
	89	* PTE in memory, iff the mapping is still on the amp_list.
	90	*
	91	* Finally, doing it under the lock lets us safely examine the page
	92	* to see if it is immutable or not, for the generic kmap_atomic() case.
	93	* If we examine it earlier we are exposed to a race where it looks
	94	* writable earlier, but becomes immutable before we write the PTE.
	95	*/
	96	static void kmap_atomic_register(struct page *page, enum km_type type,
	97	unsigned long va, pte_t *ptep, pte_t pteval)
	98	{
	99	unsigned long flags;
	100	struct atomic_mapped_page *amp;
	101
	102	flags = homecache_kpte_lock();
	103	spin_lock(&amp_lock);
	104
	105	/* With interrupts disabled, now fill in the per-cpu info. */
	106	amp = &__get_cpu_var(amps).per_type[type];
	107	amp->page = page;
	108	amp->cpu = smp_processor_id();
	109	amp->va = va;
	110
	111	/* For generic kmap_atomic(), choose the PTE writability now. */
	112	if (!pte_read(pteval))
	113	pteval = mk_pte(page, page_to_kpgprot(page));
	114
	115	list_add(&amp->list, &amp_list);
	116	set_pte(ptep, pteval);
	117	arch_flush_lazy_mmu_mode();
	118
	119	spin_unlock(&amp_lock);
	120	homecache_kpte_unlock(flags);
	121	}
	122
	123	/*
	124	* Remove a page and va, on this cpu, from the list of kmap_atomic pages.
	125	* Linear-time search, but we count on the lists being short.
	126	* We don't need to adjust the PTE under the lock (as opposed to the
	127	* kmap_atomic_register() case), since we're just unconditionally
	128	* zeroing the PTE after it's off the list.
	129	*/
	130	static void kmap_atomic_unregister(struct page *page, unsigned long va)
	131	{
	132	unsigned long flags;
	133	struct atomic_mapped_page *amp;
	134	int cpu = smp_processor_id();
	135	spin_lock_irqsave(&amp_lock, flags);
	136	list_for_each_entry(amp, &amp_list, list) {
	137	if (amp->page == page && amp->cpu == cpu && amp->va == va)
	138	break;
	139	}
	140	BUG_ON(&amp->list == &amp_list);
	141	list_del(&amp->list);
	142	spin_unlock_irqrestore(&amp_lock, flags);
	143	}
	144
145	/* Helper routine for kmap_atomic_fix_kpte(), below. */
146	static void kmap_atomic_fix_one_kpte(struct atomic_mapped_page *amp,
147	int finished)
148	{
149	pte_t *ptep = kmap_get_pte(amp->va);
150	if (!finished) {
151	set_pte(ptep, pte_mkmigrate(*ptep));
152	flush_remote(0, 0, NULL, amp->va, PAGE_SIZE, PAGE_SIZE,
153	cpumask_of(amp->cpu), NULL, 0);
154	} else {
155	/*
156	* Rewrite a default kernel PTE for this page.
157	* We rely on the fact that set_pte() writes the
158	* present+migrating bits last.
159	*/
160	pte_t pte = mk_pte(amp->page, page_to_kpgprot(amp->page));
161	set_pte(ptep, pte);
162	}
163	}
164
165	/*
166	* This routine is a helper function for homecache_fix_kpte(); see
167	* its comments for more information on the "finished" argument here.
168	*
169	* Note that we hold the lock while doing the remote flushes, which
170	* will stall any unrelated cpus trying to do kmap_atomic operations.
171	* We could just update the PTEs under the lock, and save away copies
172	* of the structs (or just the va+cpu), then flush them after we
173	* release the lock, but it seems easier just to do it all under the lock.
174	*/
175	void kmap_atomic_fix_kpte(struct page *page, int finished)
176	{
177	struct atomic_mapped_page *amp;
178	unsigned long flags;
179	spin_lock_irqsave(&amp_lock, flags);
180	list_for_each_entry(amp, &amp_list, list) {
181	if (amp->page == page)
182	kmap_atomic_fix_one_kpte(amp, finished);
183	}
184	spin_unlock_irqrestore(&amp_lock, flags);
185	}
186
187	/*
188	* kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap
189	* because the kmap code must perform a global TLB invalidation when
190	* the kmap pool wraps.
191	*
192	* Note that they may be slower than on x86 (etc.) because unlike on
193	* those platforms, we do have to take a global lock to map and unmap
194	* pages on Tile (see above).
195	*
196	* When holding an atomic kmap is is not legal to sleep, so atomic
197	* kmaps are appropriate for short, tight code paths only.
198	*/
3e4d3af5	199	void kmap_atomic_prot(struct page page, pgprot_t prot)
867e359b	200	{
867e359b	201	unsigned long vaddr;
3e4d3af5	202	int idx, type;
867e359b CM	203	pte_t *pte;
	204
	205	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
	206	pagefault_disable();
	207
	208	/* Avoid icache flushes by disallowing atomic executable mappings. */
	209	BUG_ON(pte_exec(prot));
	210
	211	if (!PageHighMem(page))
	212	return page_address(page);
	213
3e4d3af5	214	type = kmap_atomic_idx_push();
867e359b CM	215	idx = type + KM_TYPE_NR*smp_processor_id();
	216	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
	217	pte = kmap_get_pte(vaddr);
	218	BUG_ON(!pte_none(*pte));
	219
	220	/* Register that this page is mapped atomically on this cpu. */
	221	kmap_atomic_register(page, type, vaddr, pte, mk_pte(page, prot));
	222
	223	return (void *)vaddr;
	224	}
	225	EXPORT_SYMBOL(kmap_atomic_prot);
	226
3e4d3af5	227	void __kmap_atomic(struct page page)
867e359b CM	228	{
867e359b CM	229	/* PAGE_NONE is a magic value that tells us to check immutability. */
38a6f426	230	return kmap_atomic_prot(page, PAGE_NONE);
867e359b	231	}
3e4d3af5	232	EXPORT_SYMBOL(__kmap_atomic);
867e359b	233
3e4d3af5	234	void __kunmap_atomic(void *kvaddr)
867e359b CM	235	{
867e359b CM	236	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
867e359b	237
3e4d3af5 PZ	238	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
3e4d3af5 PZ	239	vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
867e359b CM	240	pte_t *pte = kmap_get_pte(vaddr);
867e359b CM	241	pte_t pteval = *pte;
3e4d3af5 PZ	242	int idx, type;
3e4d3af5 PZ	243
20273941	244	type = kmap_atomic_idx();
3e4d3af5 PZ	245	idx = type + KM_TYPE_NR*smp_processor_id();
	246
	247	/*
	248	* Force other mappings to Oops if they try to access this pte
	249	* without first remapping it. Keeping stale mappings around
	250	* is a bad idea.
	251	*/
867e359b CM	252	BUG_ON(!pte_present(pteval) && !pte_migrating(pteval));
	253	kmap_atomic_unregister(pte_page(pteval), vaddr);
	254	kpte_clear_flush(pte, vaddr);
20273941	255	kmap_atomic_idx_pop();
867e359b CM	256	} else {
	257	/* Must be a lowmem page */
	258	BUG_ON(vaddr < PAGE_OFFSET);
	259	BUG_ON(vaddr >= (unsigned long)high_memory);
	260	}
	261
	262	arch_flush_lazy_mmu_mode();
	263	pagefault_enable();
	264	}
3e4d3af5	265	EXPORT_SYMBOL(__kunmap_atomic);
867e359b CM	266
	267	/*
	268	* This API is supposed to allow us to map memory without a "struct page".
	269	* Currently we don't support this, though this may change in the future.
	270	*/
3e4d3af5	271	void *kmap_atomic_pfn(unsigned long pfn)
867e359b	272	{
3e4d3af5	273	return kmap_atomic(pfn_to_page(pfn));
867e359b	274	}
3e4d3af5	275	void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
867e359b	276	{
3e4d3af5	277	return kmap_atomic_prot(pfn_to_page(pfn), prot);
867e359b CM	278	}
	279
	280	struct page kmap_atomic_to_page(void ptr)
	281	{
	282	pte_t *pte;
	283	unsigned long vaddr = (unsigned long)ptr;
	284
	285	if (vaddr < FIXADDR_START)
	286	return virt_to_page(ptr);
	287
	288	pte = kmap_get_pte(vaddr);
	289	return pte_page(*pte);
	290	}