diff options
Diffstat (limited to 'arch/arm/include/asm/highmem.h')
| -rw-r--r-- | arch/arm/include/asm/highmem.h | 29 |
1 files changed, 27 insertions, 2 deletions
diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h index 7080e2c8fa6..a4edd19dd3d 100644 --- a/arch/arm/include/asm/highmem.h +++ b/arch/arm/include/asm/highmem.h @@ -19,11 +19,36 @@ extern pte_t *pkmap_page_table; +extern void *kmap_high(struct page *page); +extern void kunmap_high(struct page *page); + +/* + * The reason for kmap_high_get() is to ensure that the currently kmap'd + * page usage count does not decrease to zero while we're using its + * existing virtual mapping in an atomic context. With a VIVT cache this + * is essential to do, but with a VIPT cache this is only an optimization + * so not to pay the price of establishing a second mapping if an existing + * one can be used. However, on platforms without hardware TLB maintenance + * broadcast, we simply cannot use ARCH_NEEDS_KMAP_HIGH_GET at all since + * the locking involved must also disable IRQs which is incompatible with + * the IPI mechanism used by global TLB operations. + */ #define ARCH_NEEDS_KMAP_HIGH_GET +#if defined(CONFIG_SMP) && defined(CONFIG_CPU_TLB_V6) +#undef ARCH_NEEDS_KMAP_HIGH_GET +#if defined(CONFIG_HIGHMEM) && defined(CONFIG_CPU_CACHE_VIVT) +#error "The sum of features in your kernel config cannot be supported together" +#endif +#endif -extern void *kmap_high(struct page *page); +#ifdef ARCH_NEEDS_KMAP_HIGH_GET extern void *kmap_high_get(struct page *page); -extern void kunmap_high(struct page *page); +#else +static inline void *kmap_high_get(struct page *page) +{ + return NULL; +} +#endif /* * The following functions are already defined by <linux/highmem.h> |