[patch RFC 02/15] highmem: Provide generic variant of kmap_atomic*

Thomas Gleixner
2020-09-19T09:50:37Z

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>
---
include/linux/highmem.h | 87 ++++++++++++++++++++++++++++-------
mm/Kconfig | 3 +
mm/highmem.c | 119 +++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 192 insertions(+), 17 deletions(-)

--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -31,9 +31,22 @@ static inline void invalidate_kernel_vma

#include <asm/kmap_types.h>

+/*
+ * Outside of CONFIG_HIGHMEM to support X86 32bit iomap_atomic() cruft.
+ */
+#ifdef CONFIG_KMAP_ATOMIC_GENERIC
+void *kmap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot);
+void *kmap_atomic_page_prot(struct page *page, pgprot_t prot);
+void kunmap_atomic_indexed(void *vaddr);
+# ifndef ARCH_NEEDS_KMAP_HIGH_GET
+static inline void *arch_kmap_temporary_high_get(struct page *page)
+{
+ return NULL;
+}
+# endif
+#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
@@ -81,6 +94,11 @@ static inline void kunmap(struct page *p
* be used in IRQ contexts, so in some (very limited) cases we need
* it.
*/
+
+#ifndef CONFIG_KMAP_ATOMIC_GENERIC
+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();
@@ -89,7 +107,38 @@ static inline void *kmap_atomic_prot(str
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);
+ pagefault_enable();
+}
+#else /* !CONFIG_KMAP_ATOMIC_GENERIC */
+
+static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot)
+{
+ preempt_disable();
+ return kmap_atomic_page_prot(page, prot);
+}
+
+static inline void *kmap_atomic_pfn(unsigned long pfn)
+{
+ preempt_disable();
+ return kmap_atomic_pfn_prot(pfn, kmap_prot);
+}
+
+static inline void __kunmap_atomic(void *addr)
+{
+ kumap_atomic_indexed(addr);
+}
+
+
+#endif /* CONFIG_KMAP_ATOMIC_GENERIC */
+
+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);
@@ -157,21 +206,29 @@ static inline void *kmap_atomic(struct p
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 preemption
*/
#ifdef ARCH_HAS_FLUSH_ON_KUNMAP
kunmap_flush_on_unmap(addr);
#endif
+ pagefault_enable();
}

-#define kmap_atomic_pfn(pfn) kmap_atomic(pfn_to_page(pfn))
-
#define kmap_flush_unused() do {} while(0)

#endif /* CONFIG_HIGHMEM */
@@ -213,14 +270,12 @@ static inline void kmap_atomic_idx_pop(v
* 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(); \
-} while (0)
-
+#define kunmap_atomic(addr) \
+ do { \
+ BUILD_BUG_ON(__same_type((addr), struct page *)); \
+ __kunmap_atomic(addr); \
+ preempt_enable(); \
+ } while (0)

/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -868,4 +868,7 @@ config ARCH_HAS_HUGEPD
config MAPPING_DIRTY_HELPERS
bool

+config KMAP_ATOMIC_GENERIC
+ bool
+
endmenu
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -314,6 +314,15 @@ void *kmap_high_get(struct page *page)
unlock_kmap_any(flags);
return (void*) vaddr;
}
+
+/* Unmap a temporary mapping which was obtained by kmap_high_get() */
+static void kmap_high_unmap_temporary(unsigned long vaddr)
+{
+ if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP))
+ kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
+}
+#else
+static inline void kmap_high_unmap_temporary(unsigned long vaddr) { }
#endif

/**
@@ -365,8 +374,116 @@ void kunmap_high(struct page *page)
if (need_wakeup)
wake_up(pkmap_map_wait);
}
-
EXPORT_SYMBOL(kunmap_high);
+#else
+static inline void kmap_high_unmap_temporary(unsigned long vaddr) { }
+#endif /* CONFIG_HIGHMEM */
+
+#ifdef CONFIG_KMAP_ATOMIC_GENERIC
+#ifndef arch_kmap_temp_post_map
+# define arch_kmap_temp_post_map(vaddr, pteval) do { } while (0)
+#endif
+
+#ifndef arch_kmap_temp_pre_unmap
+# define arch_kmap_temp_pre_unmap(vaddr) do { } while (0)
+#endif
+
+#ifndef arch_kmap_temp_post_unmap
+# define arch_kmap_temp_post_unmap(vaddr) do { } while (0)
+#endif
+
+#ifndef arch_kmap_temp_map_idx
+#define arch_kmap_temp_map_idx(type, pfn) kmap_temp_idx(type)
+#endif
+
+#ifndef arch_kmap_temp_unmap_idx
+#define arch_kmap_temp_unmap_idx(type, vaddr) kmap_temp_idx(type)
+#endif
+
+static inline int kmap_temp_idx(int type)
+{
+ return type + KM_TYPE_NR * 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;
+}
+
+static void *__kmap_atomic_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_temp_map_idx(kmap_atomic_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(kmap_pte - idx, pteval);
+ arch_kmap_temp_post_map(vaddr, pteval);
+ preempt_enable();
+
+ return (void *)vaddr;
+}
+
+void *kmap_atomic_pfn_prot(unsigned long pfn, pgprot_t prot)
+{
+ pagefault_disable();
+ return __kmap_atomic_pfn_prot(pfn, prot);
+}
+EXPORT_SYMBOL(kmap_atomic_pfn_prot);
+
+void *kmap_atomic_page_prot(struct page *page, pgprot_t prot)
+{
+ void *kmap;
+
+ pagefault_disable();
+ if (!PageHighMem(page))
+ return page_address(page);
+
+ /* Try kmap_high_get() if architecture has it enabled */
+ kmap = arch_kmap_temporary_high_get(page);
+ if (kmap)
+ return kmap;
+
+ return __kmap_atomic_pfn_prot(page_to_pfn(page), prot);
+}
+EXPORT_SYMBOL(kmap_atomic_page_prot);
+
+void kunmap_atomic_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_temporary(addr);
+ pagefault_enable();
+ return;
+ }
+
+ preempt_disable();
+ idx = arch_kmap_temp_unmap_idx(kmap_atomic_idx(), addr);
+ WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+
+ arch_kmap_temp_pre_unmap(addr);
+ pte_clear(&init_mm, addr, kmap_pte - idx);
+ arch_kmap_temp_post_unmap(addr);
+ kmap_atomic_idx_pop();
+ preempt_enable();
+ pagefault_enable();
+}
+EXPORT_SYMBOL(kunmap_atomic_indexed);
#endif

#if defined(HASHED_PAGE_VIRTUAL)