Message-ID: <20120907193542.GA22806@schnuecks.de>
Date:	Fri, 7 Sep 2012 21:35:42 +0200
From:	Simon Baatz <gmbnomis@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v3 09/31] arm64: Cache maintenance routines

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@....com>
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Acked-by: Tony Lindgren <tony@...mide.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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