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highmem: Provide generic variant of kmap_atomic*
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The kmap_atomic* interfaces in all architectures are pretty much the same
except for post map operations (flush) and pre- and post unmap operations.

Provide a generic variant for that.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20201103095857.175939340@linutronix.de
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Thomas Gleixner committed Nov 6, 2020
1 parent 4f8b96c commit 298fa1a
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Showing 3 changed files with 211 additions and 18 deletions.
82 changes: 66 additions & 16 deletions include/linux/highmem.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,16 @@ static inline void invalidate_kernel_vmap_range(void *vaddr, int size)

#include <asm/kmap_types.h>

/*
* Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft.
*/
#ifdef CONFIG_KMAP_LOCAL
void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot);
void *__kmap_local_page_prot(struct page *page, pgprot_t prot);
void kunmap_local_indexed(void *vaddr);
#endif

#ifdef CONFIG_HIGHMEM
extern void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
extern void kunmap_atomic_high(void *kvaddr);
#include <asm/highmem.h>

#ifndef ARCH_HAS_KMAP_FLUSH_TLB
Expand Down Expand Up @@ -81,6 +88,11 @@ static inline void kunmap(struct page *page)
* be used in IRQ contexts, so in some (very limited) cases we need
* it.
*/

#ifndef CONFIG_KMAP_LOCAL
void *kmap_atomic_high_prot(struct page *page, pgprot_t prot);
void kunmap_atomic_high(void *kvaddr);

static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
{
preempt_disable();
Expand All @@ -89,7 +101,38 @@ static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
return page_address(page);
return kmap_atomic_high_prot(page, prot);
}
#define kmap_atomic(page) kmap_atomic_prot(page, kmap_prot)

static inline void __kunmap_atomic(void *vaddr)
{
kunmap_atomic_high(vaddr);
}
#else /* !CONFIG_KMAP_LOCAL */

static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
{
preempt_disable();
pagefault_disable();
return __kmap_local_page_prot(page, prot);
}

static inline void *kmap_atomic_pfn(unsigned long pfn)
{
preempt_disable();
pagefault_disable();
return __kmap_local_pfn_prot(pfn, kmap_prot);
}

static inline void __kunmap_atomic(void *addr)
{
kunmap_local_indexed(addr);
}

#endif /* CONFIG_KMAP_LOCAL */

static inline void *kmap_atomic(struct page *page)
{
return kmap_atomic_prot(page, kmap_prot);
}

/* declarations for linux/mm/highmem.c */
unsigned int nr_free_highpages(void);
Expand Down Expand Up @@ -147,25 +190,33 @@ static inline void *kmap_atomic(struct page *page)
pagefault_disable();
return page_address(page);
}
#define kmap_atomic_prot(page, prot) kmap_atomic(page)

static inline void kunmap_atomic_high(void *addr)
static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
{
return kmap_atomic(page);
}

static inline void *kmap_atomic_pfn(unsigned long pfn)
{
return kmap_atomic(pfn_to_page(pfn));
}

static inline void __kunmap_atomic(void *addr)
{
/*
* Mostly nothing to do in the CONFIG_HIGHMEM=n case as kunmap_atomic()
* handles re-enabling faults + preemption
* handles re-enabling faults and preemption
*/
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
kunmap_flush_on_unmap(addr);
#endif
}

#define kmap_atomic_pfn(pfn) kmap_atomic(pfn_to_page(pfn))

#define kmap_flush_unused() do {} while(0)

#endif /* CONFIG_HIGHMEM */

#if !defined(CONFIG_KMAP_LOCAL)
#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)

DECLARE_PER_CPU(int, __kmap_atomic_idx);
Expand Down Expand Up @@ -196,22 +247,21 @@ static inline void kmap_atomic_idx_pop(void)
__this_cpu_dec(__kmap_atomic_idx);
#endif
}

#endif
#endif

/*
* Prevent people trying to call kunmap_atomic() as if it were kunmap()
* kunmap_atomic() should get the return value of kmap_atomic, not the page.
*/
#define kunmap_atomic(addr) \
do { \
BUILD_BUG_ON(__same_type((addr), struct page *)); \
kunmap_atomic_high(addr); \
pagefault_enable(); \
preempt_enable(); \
#define kunmap_atomic(__addr) \
do { \
BUILD_BUG_ON(__same_type((__addr), struct page *)); \
__kunmap_atomic(__addr); \
pagefault_enable(); \
preempt_enable(); \
} while (0)


/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
Expand Down
3 changes: 3 additions & 0 deletions mm/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -872,4 +872,7 @@ config ARCH_HAS_HUGEPD
config MAPPING_DIRTY_HELPERS
bool

config KMAP_LOCAL
bool

endmenu
144 changes: 142 additions & 2 deletions mm/highmem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,11 @@
#include <asm/tlbflush.h>
#include <linux/vmalloc.h>

#ifndef CONFIG_KMAP_LOCAL
#if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
DEFINE_PER_CPU(int, __kmap_atomic_idx);
#endif
#endif

/*
* Virtual_count is not a pure "count".
Expand Down Expand Up @@ -365,9 +367,147 @@ void kunmap_high(struct page *page)
if (need_wakeup)
wake_up(pkmap_map_wait);
}

EXPORT_SYMBOL(kunmap_high);
#endif /* CONFIG_HIGHMEM */
#endif /* CONFIG_HIGHMEM */

#ifdef CONFIG_KMAP_LOCAL

#include <asm/kmap_size.h>

static DEFINE_PER_CPU(int, __kmap_local_idx);

static inline int kmap_local_idx_push(void)
{
int idx = __this_cpu_inc_return(__kmap_local_idx) - 1;

WARN_ON_ONCE(in_irq() && !irqs_disabled());
BUG_ON(idx >= KM_MAX_IDX);
return idx;
}

static inline int kmap_local_idx(void)
{
return __this_cpu_read(__kmap_local_idx) - 1;
}

static inline void kmap_local_idx_pop(void)
{
int idx = __this_cpu_dec_return(__kmap_local_idx);

BUG_ON(idx < 0);
}

#ifndef arch_kmap_local_post_map
# define arch_kmap_local_post_map(vaddr, pteval) do { } while (0)
#endif
#ifndef arch_kmap_local_pre_unmap
# define arch_kmap_local_pre_unmap(vaddr) do { } while (0)
#endif

#ifndef arch_kmap_local_post_unmap
# define arch_kmap_local_post_unmap(vaddr) do { } while (0)
#endif

#ifndef arch_kmap_local_map_idx
#define arch_kmap_local_map_idx(idx, pfn) kmap_local_calc_idx(idx)
#endif

#ifndef arch_kmap_local_unmap_idx
#define arch_kmap_local_unmap_idx(idx, vaddr) kmap_local_calc_idx(idx)
#endif

#ifndef arch_kmap_local_high_get
static inline void *arch_kmap_local_high_get(struct page *page)
{
return NULL;
}
#endif

/* Unmap a local mapping which was obtained by kmap_high_get() */
static inline void kmap_high_unmap_local(unsigned long vaddr)
{
#ifdef ARCH_NEEDS_KMAP_HIGH_GET
if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP))
kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
#endif
}

static inline int kmap_local_calc_idx(int idx)
{
return idx + KM_MAX_IDX * smp_processor_id();
}

static pte_t *__kmap_pte;

static pte_t *kmap_get_pte(void)
{
if (!__kmap_pte)
__kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
return __kmap_pte;
}

void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
{
pte_t pteval, *kmap_pte = kmap_get_pte();
unsigned long vaddr;
int idx;

preempt_disable();
idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
BUG_ON(!pte_none(*(kmap_pte - idx)));
pteval = pfn_pte(pfn, prot);
set_pte_at(&init_mm, vaddr, kmap_pte - idx, pteval);
arch_kmap_local_post_map(vaddr, pteval);
preempt_enable();

return (void *)vaddr;
}
EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);

void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
{
void *kmap;

if (!PageHighMem(page))
return page_address(page);

/* Try kmap_high_get() if architecture has it enabled */
kmap = arch_kmap_local_high_get(page);
if (kmap)
return kmap;

return __kmap_local_pfn_prot(page_to_pfn(page), prot);
}
EXPORT_SYMBOL(__kmap_local_page_prot);

void kunmap_local_indexed(void *vaddr)
{
unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
pte_t *kmap_pte = kmap_get_pte();
int idx;

if (addr < __fix_to_virt(FIX_KMAP_END) ||
addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
WARN_ON_ONCE(addr < PAGE_OFFSET);

/* Handle mappings which were obtained by kmap_high_get() */
kmap_high_unmap_local(addr);
return;
}

preempt_disable();
idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));

arch_kmap_local_pre_unmap(addr);
pte_clear(&init_mm, addr, kmap_pte - idx);
arch_kmap_local_post_unmap(addr);
kmap_local_idx_pop();
preempt_enable();
}
EXPORT_SYMBOL(kunmap_local_indexed);
#endif

#if defined(HASHED_PAGE_VIRTUAL)

Expand Down

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