[patch RFC 05/15] ARM: highmem: Switch to generic kmap atomic

Thomas Gleixner
2020-09-19T09:50:43Z

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-arm-kernel@lists.infradead.org
---
Note: Completely untested
---
arch/arm/Kconfig | 1
arch/arm/include/asm/highmem.h | 30 +++++++---
arch/arm/mm/Makefile | 1
arch/arm/mm/highmem.c | 121 -----------------------------------------
4 files changed, 23 insertions(+), 130 deletions(-)

--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1499,6 +1499,7 @@ config HAVE_ARCH_PFN_VALID
config HIGHMEM
bool "High Memory Support"
depends on MMU
+ select KMAP_ATOMIC_GENERIC
help
The address space of ARM processors is only 4 Gigabytes large
and it has to accommodate user address space, kernel address
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -46,19 +46,33 @@ extern pte_t *pkmap_page_table;

#ifdef ARCH_NEEDS_KMAP_HIGH_GET
extern void *kmap_high_get(struct page *page);
+
+#ifdef CONFIG_DEBUG_HIGHMEM
+extern void *arch_kmap_temporary_high_get(struct page *page);
#else
+static inline void *arch_kmap_temporary_high_get(struct page *page)
+{
+ return kmap_high_get(page);
+}
+#endif /* !CONFIG_DEBUG_HIGHMEM */
+
+#else /* ARCH_NEEDS_KMAP_HIGH_GET */
static inline void *kmap_high_get(struct page *page)
{
return NULL;
}
-#endif
+#endif /* !ARCH_NEEDS_KMAP_HIGH_GET */

-/*
- * The following functions are already defined by <linux/highmem.h>
- * when CONFIG_HIGHMEM is not set.
- */
-#ifdef CONFIG_HIGHMEM
-extern void *kmap_atomic_pfn(unsigned long pfn);
-#endif
+#define arch_kmap_temp_post_map(vaddr, pteval) \
+ local_flush_tlb_kernel_page(vaddr)
+
+#define arch_kmap_temp_pre_unmap(vaddr) \
+do { \
+ if (cache_is_vivt()) \
+ __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE); \
+} while (0)
+
+#define arch_kmap_temp_post_unmap(vaddr) \
+ local_flush_tlb_kernel_page(vaddr)

#endif
--- a/arch/arm/mm/Makefile
+++ b/arch/arm/mm/Makefile
@@ -19,7 +19,6 @@ obj-$(CONFIG_MODULES) += proc-syms.o
obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o

obj-$(CONFIG_ALIGNMENT_TRAP) += alignment.o
-obj-$(CONFIG_HIGHMEM) += highmem.o
obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
obj-$(CONFIG_ARM_PV_FIXUP) += pv-fixup-asm.o

--- a/arch/arm/mm/highmem.c
+++ /dev/null
@@ -1,121 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * arch/arm/mm/highmem.c -- ARM highmem support
- *
- * Author: Nicolas Pitre
- * Created: september 8, 2008
- * Copyright: Marvell Semiconductors Inc.
- */
-
-#include <linux/module.h>
-#include <linux/highmem.h>
-#include <linux/interrupt.h>
-#include <asm/fixmap.h>
-#include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
-#include "mm.h"
-
-static inline void set_fixmap_pte(int idx, pte_t pte)
-{
- unsigned long vaddr = __fix_to_virt(idx);
- pte_t *ptep = virt_to_kpte(vaddr);
-
- set_pte_ext(ptep, pte, 0);
- local_flush_tlb_kernel_page(vaddr);
-}
-
-static inline pte_t get_fixmap_pte(unsigned long vaddr)
-{
- pte_t *ptep = virt_to_kpte(vaddr);
-
- return *ptep;
-}
-
-void *kmap_atomic_high_prot(struct page *page, pgprot_t prot)
-{
- unsigned int idx;
- unsigned long vaddr;
- void *kmap;
- int type;
-
-#ifdef CONFIG_DEBUG_HIGHMEM
- /*
- * There is no cache coherency issue when non VIVT, so force the
- * dedicated kmap usage for better debugging purposes in that case.
- */
- if (!cache_is_vivt())
- kmap = NULL;
- else
-#endif
- kmap = kmap_high_get(page);
- if (kmap)
- return kmap;
-
- type = kmap_atomic_idx_push();
-
- idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
- vaddr = __fix_to_virt(idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
- /*
- * With debugging enabled, kunmap_atomic forces that entry to 0.
- * Make sure it was indeed properly unmapped.
- */
- BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
-#endif
- /*
- * When debugging is off, kunmap_atomic leaves the previous mapping
- * in place, so the contained TLB flush ensures the TLB is updated
- * with the new mapping.
- */
- set_fixmap_pte(idx, mk_pte(page, prot));
-
- return (void *)vaddr;
-}
-EXPORT_SYMBOL(kmap_atomic_high_prot);
-
-void kunmap_atomic_high(void *kvaddr)
-{
- unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
- int idx, type;
-
- if (kvaddr >= (void *)FIXADDR_START) {
- type = kmap_atomic_idx();
- idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
-
- if (cache_is_vivt())
- __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
-#ifdef CONFIG_DEBUG_HIGHMEM
- BUG_ON(vaddr != __fix_to_virt(idx));
- set_fixmap_pte(idx, __pte(0));
-#else
- (void) idx; /* to kill a warning */
-#endif
- kmap_atomic_idx_pop();
- } else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
- /* this address was obtained through kmap_high_get() */
- kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
- }
-}
-EXPORT_SYMBOL(kunmap_atomic_high);
-
-void *kmap_atomic_pfn(unsigned long pfn)
-{
- unsigned long vaddr;
- int idx, type;
- struct page *page = pfn_to_page(pfn);
-
- preempt_disable();
- pagefault_disable();
- if (!PageHighMem(page))
- return page_address(page);
-
- type = kmap_atomic_idx_push();
- idx = FIX_KMAP_BEGIN + type + KM_TYPE_NR * smp_processor_id();
- vaddr = __fix_to_virt(idx);
-#ifdef CONFIG_DEBUG_HIGHMEM
- BUG_ON(!pte_none(get_fixmap_pte(vaddr)));
-#endif
- set_fixmap_pte(idx, pfn_pte(pfn, kmap_prot));
-
- return (void *)vaddr;
-}