/*
* 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);
}
