Re: [PATCH v3 09/31] arm64: Cache maintenance routines

From: Simon Baatz
Date: Fri Sep 07 2012 - 15:35:54 EST

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Hi Catalin,

On Fri, Sep 07, 2012 at 05:26:44PM +0100, Catalin Marinas wrote:
> The patch adds functionality required for cache maintenance. The AArch64
> architecture mandates non-aliasing VIPT or PIPT D-cache and VIPT (may
> have aliases) or ASID-tagged VIVT I-cache. Cache maintenance operations
> are automatically broadcast in hardware between CPUs.
>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Acked-by: Tony Lindgren <tony@xxxxxxxxxxx>
> ---
> arch/arm64/include/asm/cache.h | 32 +++++
> arch/arm64/include/asm/cacheflush.h | 168 +++++++++++++++++++++++
> arch/arm64/include/asm/cachetype.h | 48 +++++++
> arch/arm64/mm/cache.S | 251 +++++++++++++++++++++++++++++++++++
> arch/arm64/mm/flush.c | 138 +++++++++++++++++++
> 5 files changed, 637 insertions(+), 0 deletions(-)
> create mode 100644 arch/arm64/include/asm/cache.h
> create mode 100644 arch/arm64/include/asm/cacheflush.h
> create mode 100644 arch/arm64/include/asm/cachetype.h
> create mode 100644 arch/arm64/mm/cache.S
> create mode 100644 arch/arm64/mm/flush.c
>
> diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
> new file mode 100644
> index 0000000..390308a
> --- /dev/null
> +++ b/arch/arm64/include/asm/cache.h
> @@ -0,0 +1,32 @@
> +/*
> + * Copyright (C) 2012 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef __ASM_CACHE_H
> +#define __ASM_CACHE_H
> +
> +#define L1_CACHE_SHIFT 6
> +#define L1_CACHE_BYTES (1 << L1_CACHE_SHIFT)
> +
> +/*
> + * Memory returned by kmalloc() may be used for DMA, so we must make
> + * sure that all such allocations are cache aligned. Otherwise,
> + * unrelated code may cause parts of the buffer to be read into the
> + * cache before the transfer is done, causing old data to be seen by
> + * the CPU.
> + */
> +#define ARCH_DMA_MINALIGN L1_CACHE_BYTES
> +#define ARCH_SLAB_MINALIGN 8
> +
> +#endif
> diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
> new file mode 100644
> index 0000000..0bb9853
> --- /dev/null
> +++ b/arch/arm64/include/asm/cacheflush.h
> @@ -0,0 +1,168 @@
> +/*
> + * Based on arch/arm/include/asm/cacheflush.h
> + *
> + * Copyright (C) 1999-2002 Russell King.
> + * Copyright (C) 2012 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef __ASM_CACHEFLUSH_H
> +#define __ASM_CACHEFLUSH_H
> +
> +#include <linux/mm.h>
> +
> +/*
> + * This flag is used to indicate that the page pointed to by a pte is clean
> + * and does not require cleaning before returning it to the user.
> + */
> +#define PG_dcache_clean PG_arch_1
> +
> +/*
> + * MM Cache Management
> + * ===================
> + *
> + * The arch/arm64/mm/cache.S implements these methods.
> + *
> + * Start addresses are inclusive and end addresses are exclusive; start
> + * addresses should be rounded down, end addresses up.
> + *
> + * See Documentation/cachetlb.txt for more information. Please note that
> + * the implementation assumes non-aliasing VIPT D-cache and (aliasing)
> + * VIPT or ASID-tagged VIVT I-cache.
> + *
> + * flush_cache_all()
> + *
> + * Unconditionally clean and invalidate the entire cache.
> + *
> + * flush_cache_mm(mm)
> + *
> + * Clean and invalidate all user space cache entries
> + * before a change of page tables.
> + *
> + * flush_icache_range(start, end)
> + *
> + * Ensure coherency between the I-cache and the D-cache in the
> + * region described by start, end.
> + * - start - virtual start address
> + * - end - virtual end address
> + *
> + * __flush_cache_user_range(start, end)
> + *
> + * Ensure coherency between the I-cache and the D-cache in the
> + * region described by start, end.
> + * - start - virtual start address
> + * - end - virtual end address
> + *
> + * __flush_dcache_area(kaddr, size)
> + *
> + * Ensure that the data held in page is written back.
> + * - kaddr - page address
> + * - size - region size
> + */
> +extern void flush_cache_all(void);
> +extern void flush_cache_mm(struct mm_struct *mm);
> +extern void flush_cache_range(struct vm_area_struct *vma, unsigned long start, unsigned long end);
> +extern void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr, unsigned long pfn);
> +extern void flush_icache_range(unsigned long start, unsigned long end);
> +extern void __flush_dcache_area(void *addr, size_t len);
> +extern void __flush_cache_user_range(unsigned long start, unsigned long end);
> +
> +/*
> + * These are private to the dma-mapping API. Do not use directly.
> + * Their sole purpose is to ensure that data held in the cache
> + * is visible to DMA, or data written by DMA to system memory is
> + * visible to the CPU.
> + */
> +extern void dmac_map_area(const void *, size_t, int);
> +extern void dmac_unmap_area(const void *, size_t, int);
> +extern void dmac_flush_range(const void *, const void *);
> +
> +/*
> + * Copy user data from/to a page which is mapped into a different
> + * processes address space. Really, we want to allow our "user
> + * space" model to handle this.
> + */
> +extern void copy_to_user_page(struct vm_area_struct *, struct page *,
> + unsigned long, void *, const void *, unsigned long);
> +#define copy_from_user_page(vma, page, vaddr, dst, src, len) \
> + do { \
> + memcpy(dst, src, len); \
> + } while (0)
> +
> +#define flush_cache_dup_mm(mm) flush_cache_mm(mm)
> +
> +/*
> + * flush_dcache_page is used when the kernel has written to the page
> + * cache page at virtual address page->virtual.
> + *
> + * If this page isn't mapped (ie, page_mapping == NULL), or it might
> + * have userspace mappings, then we _must_ always clean + invalidate
> + * the dcache entries associated with the kernel mapping.
> + *
> + * Otherwise we can defer the operation, and clean the cache when we are
> + * about to change to user space. This is the same method as used on SPARC64.
> + * See update_mmu_cache for the user space part.
> + */
> +#define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 1
> +extern void flush_dcache_page(struct page *);
> +
> +static inline void __flush_icache_all(void)
> +{
> + asm("ic ialluis");
> +}
> +
> +#define ARCH_HAS_FLUSH_ANON_PAGE
> +static inline void flush_anon_page(struct vm_area_struct *vma,
> + struct page *page, unsigned long vmaddr)
> +{
> + extern void __flush_anon_page(struct vm_area_struct *vma,
> + struct page *, unsigned long);
> + if (PageAnon(page))
> + __flush_anon_page(vma, page, vmaddr);

__flush_anon_page() does nothing. Shouldn't this be removed as well?

> +}
> +
> +#define flush_dcache_mmap_lock(mapping) \
> + spin_lock_irq(&(mapping)->tree_lock)
> +#define flush_dcache_mmap_unlock(mapping) \
> + spin_unlock_irq(&(mapping)->tree_lock)
> +
> +#define flush_icache_user_range(vma,page,addr,len) \
> + flush_dcache_page(page)
> +
> +/*
> + * We don't appear to need to do anything here. In fact, if we did, we'd
> + * duplicate cache flushing elsewhere performed by flush_dcache_page().
> + */
> +#define flush_icache_page(vma,page) do { } while (0)
> +
> +/*
> + * flush_cache_vmap() is used when creating mappings (eg, via vmap,
> + * vmalloc, ioremap etc) in kernel space for pages. On non-VIPT
> + * caches, since the direct-mappings of these pages may contain cached
> + * data, we need to do a full cache flush to ensure that writebacks
> + * don't corrupt data placed into these pages via the new mappings.
> + */
> +static inline void flush_cache_vmap(unsigned long start, unsigned long end)
> +{
> + /*
> + * set_pte_at() called from vmap_pte_range() does not
> + * have a DSB after cleaning the cache line.
> + */
> + dsb();
> +}
> +
> +static inline void flush_cache_vunmap(unsigned long start, unsigned long end)
> +{
> +}
> +
> +#endif
> diff --git a/arch/arm64/include/asm/cachetype.h b/arch/arm64/include/asm/cachetype.h
> new file mode 100644
> index 0000000..85f5f51
> --- /dev/null
> +++ b/arch/arm64/include/asm/cachetype.h
> @@ -0,0 +1,48 @@
> +/*
> + * Copyright (C) 2012 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef __ASM_CACHETYPE_H
> +#define __ASM_CACHETYPE_H
> +
> +#include <asm/cputype.h>
> +
> +#define CTR_L1IP_SHIFT 14
> +#define CTR_L1IP_MASK 3
> +
> +#define ICACHE_POLICY_RESERVED 0
> +#define ICACHE_POLICY_AIVIVT 1
> +#define ICACHE_POLICY_VIPT 2
> +#define ICACHE_POLICY_PIPT 3
> +
> +static inline u32 icache_policy(void)
> +{
> + return (read_cpuid_cachetype() >> CTR_L1IP_SHIFT) & CTR_L1IP_MASK;
> +}
> +
> +/*
> + * Whilst the D-side always behaves as PIPT on AArch64, aliasing is
> + * permitted in the I-cache.
> + */
> +static inline int icache_is_aliasing(void)
> +{
> + return icache_policy() != ICACHE_POLICY_PIPT;
> +}
> +
> +static inline int icache_is_aivivt(void)
> +{
> + return icache_policy() == ICACHE_POLICY_AIVIVT;
> +}
> +
> +#endif /* __ASM_CACHETYPE_H */
> diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
> new file mode 100644
> index 0000000..3df0aa7
> --- /dev/null
> +++ b/arch/arm64/mm/cache.S
> @@ -0,0 +1,251 @@
> +/*
> + * Cache maintenance
> + *
> + * Copyright (C) 2001 Deep Blue Solutions Ltd.
> + * Copyright (C) 2012 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/linkage.h>
> +#include <linux/init.h>
> +#include <asm/assembler.h>
> +
> +#include "proc-macros.S"
> +
> +/*
> + * __flush_dcache_all()
> + *
> + * Flush the whole D-cache.
> + *
> + * Corrupted registers: x0-x7, x9-x11
> + */
> +ENTRY(__flush_dcache_all)
> + dsb sy // ensure ordering with previous memory accesses
> + mrs x0, clidr_el1 // read clidr
> + and x3, x0, #0x7000000 // extract loc from clidr
> + lsr x3, x3, #23 // left align loc bit field
> + cbz x3, finished // if loc is 0, then no need to clean
> + mov x10, #0 // start clean at cache level 0
> +loop1:
> + add x2, x10, x10, lsr #1 // work out 3x current cache level
> + lsr x1, x0, x2 // extract cache type bits from clidr
> + and x1, x1, #7 // mask of the bits for current cache only
> + cmp x1, #2 // see what cache we have at this level
> + b.lt skip // skip if no cache, or just i-cache
> + save_and_disable_irqs x9 // make CSSELR and CCSIDR access atomic
> + msr csselr_el1, x10 // select current cache level in csselr
> + isb // isb to sych the new cssr&csidr
> + mrs x1, ccsidr_el1 // read the new ccsidr
> + restore_irqs x9
> + and x2, x1, #7 // extract the length of the cache lines
> + add x2, x2, #4 // add 4 (line length offset)
> + mov x4, #0x3ff
> + and x4, x4, x1, lsr #3 // find maximum number on the way size
> + clz x5, x4 // find bit position of way size increment
> + mov x7, #0x7fff
> + and x7, x7, x1, lsr #13 // extract max number of the index size
> +loop2:
> + mov x9, x4 // create working copy of max way size
> +loop3:
> + lsl x6, x9, x5
> + orr x11, x10, x6 // factor way and cache number into x11
> + lsl x6, x7, x2
> + orr x11, x11, x6 // factor index number into x11
> + dc cisw, x11 // clean & invalidate by set/way
> + subs x9, x9, #1 // decrement the way
> + b.ge loop3
> + subs x7, x7, #1 // decrement the index
> + b.ge loop2
> +skip:
> + add x10, x10, #2 // increment cache number
> + cmp x3, x10
> + b.gt loop1
> +finished:
> + mov x10, #0 // swith back to cache level 0
> + msr csselr_el1, x10 // select current cache level in csselr
> + dsb sy
> + isb
> + ret
> +ENDPROC(__flush_dcache_all)
> +
> +/*
> + * flush_cache_all()
> + *
> + * Flush the entire cache system. The data cache flush is now achieved
> + * using atomic clean / invalidates working outwards from L1 cache. This
> + * is done using Set/Way based cache maintainance instructions. The
> + * instruction cache can still be invalidated back to the point of
> + * unification in a single instruction.
> + */
> +ENTRY(flush_cache_all)
> + mov x12, lr
> + bl __flush_dcache_all
> + mov x0, #0
> + ic ialluis // I+BTB cache invalidate
> + ret x12
> +ENDPROC(flush_cache_all)
> +
> +/*
> + * flush_icache_range(start,end)
> + *
> + * Ensure that the I and D caches are coherent within specified region.
> + * This is typically used when code has been written to a memory region,
> + * and will be executed.
> + *
> + * - start - virtual start address of region
> + * - end - virtual end address of region
> + */
> +ENTRY(flush_icache_range)
> + /* FALLTHROUGH */
> +
> +/*
> + * __flush_cache_user_range(start,end)
> + *
> + * Ensure that the I and D caches are coherent within specified region.
> + * This is typically used when code has been written to a memory region,
> + * and will be executed.
> + *
> + * - start - virtual start address of region
> + * - end - virtual end address of region
> + */
> +ENTRY(__flush_cache_user_range)
> + dcache_line_size x2, x3
> + sub x3, x2, #1
> + bic x4, x0, x3
> +1:
> +USER(9f, dc cvau, x4 ) // clean D line to PoU
> + add x4, x4, x2
> + cmp x4, x1
> + b.lo 1b
> + dsb sy
> +
> + icache_line_size x2, x3
> + sub x3, x2, #1
> + bic x4, x0, x3
> +1:
> +USER(9f, ic ivau, x4 ) // invalidate I line PoU
> + add x4, x4, x2
> + cmp x4, x1
> + b.lo 1b
> +9: // ignore any faulting cache operation
> + dsb sy
> + isb
> + ret
> +ENDPROC(flush_icache_range)
> +ENDPROC(__flush_cache_user_range)
> +
> +/*
> + * __flush_kern_dcache_page(kaddr)

Should be: __flush_dcache_area(kaddr,size)

> + *
> + * Ensure that the data held in the page kaddr is written back to the
> + * page in question.

s/page/area

> + *
> + * - kaddr - kernel address
> + * - size - size in question
> + */
> +ENTRY(__flush_dcache_area)
> + dcache_line_size x2, x3
> + add x1, x0, x1
> + sub x3, x2, #1
> + bic x0, x0, x3
> +1: dc civac, x0 // clean & invalidate D line / unified line
> + add x0, x0, x2
> + cmp x0, x1
> + b.lo 1b
> + dsb sy
> + ret
> +ENDPROC(__flush_dcache_area)
> +
> +/*
> + * dmac_inv_range(start,end)
> + *
> + * Invalidate the data cache within the specified region; we will be
> + * performing a DMA operation in this region and we want to purge old
> + * data in the cache.
> + *
> + * - start - virtual start address of region
> + * - end - virtual end address of region
> + */
> +ENTRY(dmac_inv_range)
> + dcache_line_size x2, x3
> + sub x3, x2, #1
> + bic x0, x0, x3
> + bic x1, x1, x3
> +1: dc ivac, x0 // invalidate D / U line
> + add x0, x0, x2
> + cmp x0, x1
> + b.lo 1b
> + dsb sy
> + ret
> +ENDPROC(dmac_inv_range)
> +
> +/*
> + * dmac_clean_range(start,end)
> + * - start - virtual start address of region
> + * - end - virtual end address of region
> + */
> +ENTRY(dmac_clean_range)
> + dcache_line_size x2, x3
> + sub x3, x2, #1
> + bic x0, x0, x3
> +1: dc cvac, x0 // clean D / U line
> + add x0, x0, x2
> + cmp x0, x1
> + b.lo 1b
> + dsb sy
> + ret
> +ENDPROC(dmac_clean_range)
> +
> +/*
> + * dmac_flush_range(start,end)
> + * - start - virtual start address of region
> + * - end - virtual end address of region
> + */
> +ENTRY(dmac_flush_range)
> + dcache_line_size x2, x3
> + sub x3, x2, #1
> + bic x0, x0, x3
> +1: dc civac, x0 // clean & invalidate D / U line
> + add x0, x0, x2
> + cmp x0, x1
> + b.lo 1b
> + dsb sy
> + ret
> +ENDPROC(dmac_flush_range)
> +
> +/*
> + * dmac_map_area(start, size, dir)
> + * - start - kernel virtual start address
> + * - size - size of region
> + * - dir - DMA direction
> + */
> +ENTRY(dmac_map_area)
> + add x1, x1, x0
> + cmp x2, #DMA_FROM_DEVICE
> + b.eq dmac_inv_range
> + b dmac_clean_range
> +ENDPROC(dmac_map_area)
> +
> +/*
> + * dmac_unmap_area(start, size, dir)
> + * - start - kernel virtual start address
> + * - size - size of region
> + * - dir - DMA direction
> + */
> +ENTRY(dmac_unmap_area)
> + add x1, x1, x0
> + cmp x2, #DMA_TO_DEVICE
> + b.ne dmac_inv_range
> + ret
> +ENDPROC(dmac_unmap_area)
> diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
> new file mode 100644
> index 0000000..6138d86
> --- /dev/null
> +++ b/arch/arm64/mm/flush.c
> @@ -0,0 +1,138 @@
> +/*
> + * Based on arch/arm/mm/flush.c
> + *
> + * Copyright (C) 1995-2002 Russell King
> + * Copyright (C) 2012 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * 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. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/export.h>
> +#include <linux/mm.h>
> +#include <linux/pagemap.h>
> +
> +#include <asm/cacheflush.h>
> +#include <asm/cachetype.h>
> +#include <asm/tlbflush.h>
> +
> +#include "mm.h"
> +
> +void flush_cache_mm(struct mm_struct *mm)
> +{
> +}
> +
> +void flush_cache_range(struct vm_area_struct *vma, unsigned long start,
> + unsigned long end)
> +{
> + if (vma->vm_flags & VM_EXEC)
> + __flush_icache_all();
> +}
> +
> +void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr,
> + unsigned long pfn)
> +{
> +}
> +
> +static void flush_ptrace_access(struct vm_area_struct *vma, struct page *page,
> + unsigned long uaddr, void *kaddr,
> + unsigned long len)
> +{
> + if (vma->vm_flags & VM_EXEC) {
> + unsigned long addr = (unsigned long)kaddr;
> + if (icache_is_aliasing()) {
> + __flush_dcache_area(kaddr, len);
> + __flush_icache_all();
> + } else {
> + flush_icache_range(addr, addr + len);
> + }
> + }
> +}
> +
> +/*
> + * Copy user data from/to a page which is mapped into a different processes
> + * address space. Really, we want to allow our "user space" model to handle
> + * this.
> + *
> + * Note that this code needs to run on the current CPU.
> + */
> +void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
> + unsigned long uaddr, void *dst, const void *src,
> + unsigned long len)
> +{
> +#ifdef CONFIG_SMP
> + preempt_disable();
> +#endif
> + memcpy(dst, src, len);
> + flush_ptrace_access(vma, page, uaddr, dst, len);
> +#ifdef CONFIG_SMP
> + preempt_enable();
> +#endif
> +}
> +
> +void __flush_dcache_page(struct address_space *mapping, struct page *page)
> +{
> + __flush_dcache_area(page_address(page), PAGE_SIZE);
> +}
> +
> +void __sync_icache_dcache(pte_t pte)
> +{
> + unsigned long pfn;
> + struct page *page;
> +
> + pfn = pte_pfn(pte);
> + if (!pfn_valid(pfn))
> + return;
> +
> + page = pfn_to_page(pfn);
> + if (!test_and_set_bit(PG_dcache_clean, &page->flags))
> + __flush_dcache_page(NULL, page);
> + __flush_icache_all();
> +}
> +
> +/*
> + * Ensure cache coherency between kernel mapping and userspace mapping of this
> + * page.
> + */
> +void flush_dcache_page(struct page *page)
> +{
> + struct address_space *mapping;
> +
> + /*
> + * The zero page is never written to, so never has any dirty cache
> + * lines, and therefore never needs to be flushed.
> + */
> + if (page == ZERO_PAGE(0))
> + return;
> +
> + mapping = page_mapping(page);
> +
> + if (mapping && !mapping_mapped(mapping))
> + clear_bit(PG_dcache_clean, &page->flags);
> + else {
> + __flush_dcache_page(mapping, page);
> + if (mapping)
> + __flush_icache_all();

Is this necessary to ensure I/D coherency? Then, I would have
expected

if (mapping) {
__flush_dcache_page(mapping, page);
__flush_icache_all();
}

similar to __sync_icache_dcache() above.

What is the reason why the D-cache flush is done in different
cases than the following I-cache flush?

> + set_bit(PG_dcache_clean, &page->flags);
> + }
> +}
> +EXPORT_SYMBOL(flush_dcache_page);
> +
> +void __flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned long vmaddr)
> +{
> +}

Note that the __flush_dcache_page(mapping, page) in
flush_dcache_page() above is called when page is an anonymous page
(since mapping == NULL in this case). If the call to
__flush_dcache_page() is right above, it should be needed
here as well?

> +
> +/*
> + * Additional functions defined in assembly.
> + */
> +EXPORT_SYMBOL(flush_cache_all);
> +EXPORT_SYMBOL(flush_icache_range);
>
>

- Simon
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