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.dea...@arm.com>
> Signed-off-by: Catalin Marinas <catalin.mari...@arm.com>
> Acked-by: Tony Lindgren <t...@atomide.com>
> ---
>  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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