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linux/include/asm-sh/pgtable_64.h
Nick Piggin 7e675137a8 mm: introduce pte_special pte bit 
s390 for one, cannot implement VM_MIXEDMAP with pfn_valid, due to their memory
model (which is more dynamic than most).  Instead, they had proposed to
implement it with an additional path through vm_normal_page(), using a bit in
the pte to determine whether or not the page should be refcounted:

vm_normal_page()
{
	...
        if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
                if (vma->vm_flags & VM_MIXEDMAP) {
#ifdef s390
			if (!mixedmap_refcount_pte(pte))
				return NULL;
#else
                        if (!pfn_valid(pfn))
                                return NULL;
#endif
                        goto out;
                }
	...
}

This is fine, however if we are allowed to use a bit in the pte to determine
refcountedness, we can use that to _completely_ replace all the vma based
schemes.  So instead of adding more cases to the already complex vma-based
scheme, we can have a clearly seperate and simple pte-based scheme (and get
slightly better code generation in the process):

vm_normal_page()
{
#ifdef s390
	if (!mixedmap_refcount_pte(pte))
		return NULL;
	return pte_page(pte);
#else
	...
#endif
}

And finally, we may rather make this concept usable by any architecture rather
than making it s390 only, so implement a new type of pte state for this.
Unfortunately the old vma based code must stay, because some architectures may
not be able to spare pte bits.  This makes vm_normal_page a little bit more
ugly than we would like, but the 2 cases are clearly seperate.

So introduce a pte_special pte state, and use it in mm/memory.c.  It is
currently a noop for all architectures, so this doesn't actually result in any
compiled code changes to mm/memory.o.

BTW:
I haven't put vm_normal_page() into arch code as-per an earlier suggestion.
The reason is that, regardless of where vm_normal_page is actually
implemented, the *abstraction* is still exactly the same. Also, while it
depends on whether the architecture has pte_special or not, that is the
only two possible cases, and it really isn't an arch specific function --
the role of the arch code should be to provide primitive functions and
accessors with which to build the core code; pte_special does that. We do
not want architectures to know or care about vm_normal_page itself, and
we definitely don't want them being able to invent something new there
out of sight of mm/ code. If we made vm_normal_page an arch function, then
we have to make vm_insert_mixed (next patch) an arch function too. So I
don't think moving it to arch code fundamentally improves any abstractions,
while it does practically make the code more difficult to follow, for both
mm and arch developers, and easier to misuse.

[akpm@linux-foundation.org: build fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Cc: Jared Hulbert <jaredeh@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-28 08:58:23 -07:00

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#ifndef __ASM_SH_PGTABLE_64_H
#define __ASM_SH_PGTABLE_64_H
/*
* include/asm-sh/pgtable_64.h
*
* This file contains the functions and defines necessary to modify and use
* the SuperH page table tree.
*
* Copyright (C) 2000, 2001 Paolo Alberelli
* Copyright (C) 2003, 2004 Paul Mundt
* Copyright (C) 2003, 2004 Richard Curnow
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/threads.h>
#include <asm/processor.h>
#include <asm/page.h>
/*
* Error outputs.
*/
#define pte_ERROR(e) \
printk("%s:%d: bad pte %016Lx.\n", __FILE__, __LINE__, pte_val(e))
#define pgd_ERROR(e) \
printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
/*
* Table setting routines. Used within arch/mm only.
*/
#define set_pmd(pmdptr, pmdval) (*(pmdptr) = pmdval)
static __inline__ void set_pte(pte_t *pteptr, pte_t pteval)
{
unsigned long long x = ((unsigned long long) pteval.pte_low);
unsigned long long *xp = (unsigned long long *) pteptr;
/*
* Sign-extend based on NPHYS.
*/
*(xp) = (x & NPHYS_SIGN) ? (x | NPHYS_MASK) : x;
}
#define set_pte_at(mm,addr,ptep,pteval) set_pte(ptep,pteval)
static __inline__ void pmd_set(pmd_t *pmdp,pte_t *ptep)
{
pmd_val(*pmdp) = (unsigned long) ptep;
}
/*
* PGD defines. Top level.
*/
/* To find an entry in a generic PGD. */
#define pgd_index(address) (((address) >> PGDIR_SHIFT) & (PTRS_PER_PGD-1))
#define __pgd_offset(address) pgd_index(address)
#define pgd_offset(mm, address) ((mm)->pgd+pgd_index(address))
/* To find an entry in a kernel PGD. */
#define pgd_offset_k(address) pgd_offset(&init_mm, address)
/*
* PMD level access routines. Same notes as above.
*/
#define _PMD_EMPTY 0x0
/* Either the PMD is empty or present, it's not paged out */
#define pmd_present(pmd_entry) (pmd_val(pmd_entry) & _PAGE_PRESENT)
#define pmd_clear(pmd_entry_p) (set_pmd((pmd_entry_p), __pmd(_PMD_EMPTY)))
#define pmd_none(pmd_entry) (pmd_val((pmd_entry)) == _PMD_EMPTY)
#define pmd_bad(pmd_entry) ((pmd_val(pmd_entry) & (~PAGE_MASK & ~_PAGE_USER)) != _KERNPG_TABLE)
#define pmd_page_vaddr(pmd_entry) \
((unsigned long) __va(pmd_val(pmd_entry) & PAGE_MASK))
#define pmd_page(pmd) \
(virt_to_page(pmd_val(pmd)))
/* PMD to PTE dereferencing */
#define pte_index(address) \
((address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1))
#define pte_offset_kernel(dir, addr) \
((pte_t *) ((pmd_val(*(dir))) & PAGE_MASK) + pte_index((addr)))
#define pte_offset_map(dir,addr) pte_offset_kernel(dir, addr)
#define pte_offset_map_nested(dir,addr) pte_offset_kernel(dir, addr)
#define pte_unmap(pte) do { } while (0)
#define pte_unmap_nested(pte) do { } while (0)
#ifndef __ASSEMBLY__
#define IOBASE_VADDR 0xff000000
#define IOBASE_END 0xffffffff
/*
* PTEL coherent flags.
* See Chapter 17 ST50 CPU Core Volume 1, Architecture.
*/
/* The bits that are required in the SH-5 TLB are placed in the h/w-defined
positions, to avoid expensive bit shuffling on every refill. The remaining
bits are used for s/w purposes and masked out on each refill.
Note, the PTE slots are used to hold data of type swp_entry_t when a page is
swapped out. Only the _PAGE_PRESENT flag is significant when the page is
swapped out, and it must be placed so that it doesn't overlap either the
type or offset fields of swp_entry_t. For x86, offset is at [31:8] and type
at [6:1], with _PAGE_PRESENT at bit 0 for both pte_t and swp_entry_t. This
scheme doesn't map to SH-5 because bit [0] controls cacheability. So bit
[2] is used for _PAGE_PRESENT and the type field of swp_entry_t is split
into 2 pieces. That is handled by SWP_ENTRY and SWP_TYPE below. */
#define _PAGE_WT 0x001 /* CB0: if cacheable, 1->write-thru, 0->write-back */
#define _PAGE_DEVICE 0x001 /* CB0: if uncacheable, 1->device (i.e. no write-combining or reordering at bus level) */
#define _PAGE_CACHABLE 0x002 /* CB1: uncachable/cachable */
#define _PAGE_PRESENT 0x004 /* software: page referenced */
#define _PAGE_FILE 0x004 /* software: only when !present */
#define _PAGE_SIZE0 0x008 /* SZ0-bit : size of page */
#define _PAGE_SIZE1 0x010 /* SZ1-bit : size of page */
#define _PAGE_SHARED 0x020 /* software: reflects PTEH's SH */
#define _PAGE_READ 0x040 /* PR0-bit : read access allowed */
#define _PAGE_EXECUTE 0x080 /* PR1-bit : execute access allowed */
#define _PAGE_WRITE 0x100 /* PR2-bit : write access allowed */
#define _PAGE_USER 0x200 /* PR3-bit : user space access allowed */
#define _PAGE_DIRTY 0x400 /* software: page accessed in write */
#define _PAGE_ACCESSED 0x800 /* software: page referenced */
/* Mask which drops software flags */
#define _PAGE_FLAGS_HARDWARE_MASK 0xfffffffffffff3dbLL
/*
* HugeTLB support
*/
#if defined(CONFIG_HUGETLB_PAGE_SIZE_64K)
#define _PAGE_SZHUGE (_PAGE_SIZE0)
#elif defined(CONFIG_HUGETLB_PAGE_SIZE_1MB)
#define _PAGE_SZHUGE (_PAGE_SIZE1)
#elif defined(CONFIG_HUGETLB_PAGE_SIZE_512MB)
#define _PAGE_SZHUGE (_PAGE_SIZE0 | _PAGE_SIZE1)
#endif
/*
* Stub out _PAGE_SZHUGE if we don't have a good definition for it,
* to make pte_mkhuge() happy.
*/
#ifndef _PAGE_SZHUGE
# define _PAGE_SZHUGE (0)
#endif
/*
* Default flags for a Kernel page.
* This is fundametally also SHARED because the main use of this define
* (other than for PGD/PMD entries) is for the VMALLOC pool which is
* contextless.
*
* _PAGE_EXECUTE is required for modules
*
*/
#define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_READ | _PAGE_WRITE | \
_PAGE_EXECUTE | \
_PAGE_CACHABLE | _PAGE_ACCESSED | _PAGE_DIRTY | \
_PAGE_SHARED)
/* Default flags for a User page */
#define _PAGE_TABLE (_KERNPG_TABLE | _PAGE_USER)
#define _PAGE_CHG_MASK (PTE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
/*
* We have full permissions (Read/Write/Execute/Shared).
*/
#define _PAGE_COMMON (_PAGE_PRESENT | _PAGE_USER | \
_PAGE_CACHABLE | _PAGE_ACCESSED)
#define PAGE_NONE __pgprot(_PAGE_CACHABLE | _PAGE_ACCESSED)
#define PAGE_SHARED __pgprot(_PAGE_COMMON | _PAGE_READ | _PAGE_WRITE | \
_PAGE_SHARED)
#define PAGE_EXECREAD __pgprot(_PAGE_COMMON | _PAGE_READ | _PAGE_EXECUTE)
/*
* We need to include PAGE_EXECUTE in PAGE_COPY because it is the default
* protection mode for the stack.
*/
#define PAGE_COPY PAGE_EXECREAD
#define PAGE_READONLY __pgprot(_PAGE_COMMON | _PAGE_READ)
#define PAGE_WRITEONLY __pgprot(_PAGE_COMMON | _PAGE_WRITE)
#define PAGE_RWX __pgprot(_PAGE_COMMON | _PAGE_READ | \
_PAGE_WRITE | _PAGE_EXECUTE)
#define PAGE_KERNEL __pgprot(_KERNPG_TABLE)
#define PAGE_KERNEL_NOCACHE \
__pgprot(_PAGE_PRESENT | _PAGE_READ | _PAGE_WRITE | \
_PAGE_EXECUTE | _PAGE_ACCESSED | \
_PAGE_DIRTY | _PAGE_SHARED)
/* Make it a device mapping for maximum safety (e.g. for mapping device
registers into user-space via /dev/map). */
#define pgprot_noncached(x) __pgprot(((x).pgprot & ~(_PAGE_CACHABLE)) | _PAGE_DEVICE)
#define pgprot_writecombine(prot) __pgprot(pgprot_val(prot) & ~_PAGE_CACHABLE)
/*
* Handling allocation failures during page table setup.
*/
extern void __handle_bad_pmd_kernel(pmd_t * pmd);
#define __handle_bad_pmd(x) __handle_bad_pmd_kernel(x)
/*
* PTE level access routines.
*
* Note1:
* It's the tree walk leaf. This is physical address to be stored.
*
* Note 2:
* Regarding the choice of _PTE_EMPTY:
We must choose a bit pattern that cannot be valid, whether or not the page
is present. bit[2]==1 => present, bit[2]==0 => swapped out. If swapped
out, bits [31:8], [6:3], [1:0] are under swapper control, so only bit[7] is
left for us to select. If we force bit[7]==0 when swapped out, we could use
the combination bit[7,2]=2'b10 to indicate an empty PTE. Alternatively, if
we force bit[7]==1 when swapped out, we can use all zeroes to indicate
empty. This is convenient, because the page tables get cleared to zero
when they are allocated.
*/
#define _PTE_EMPTY 0x0
#define pte_present(x) (pte_val(x) & _PAGE_PRESENT)
#define pte_clear(mm,addr,xp) (set_pte_at(mm, addr, xp, __pte(_PTE_EMPTY)))
#define pte_none(x) (pte_val(x) == _PTE_EMPTY)
/*
* Some definitions to translate between mem_map, PTEs, and page
* addresses:
*/
/*
* Given a PTE, return the index of the mem_map[] entry corresponding
* to the page frame the PTE. Get the absolute physical address, make
* a relative physical address and translate it to an index.
*/
#define pte_pagenr(x) (((unsigned long) (pte_val(x)) - \
__MEMORY_START) >> PAGE_SHIFT)
/*
* Given a PTE, return the "struct page *".
*/
#define pte_page(x) (mem_map + pte_pagenr(x))
/*
* Return number of (down rounded) MB corresponding to x pages.
*/
#define pages_to_mb(x) ((x) >> (20-PAGE_SHIFT))
/*
* The following have defined behavior only work if pte_present() is true.
*/
static inline int pte_dirty(pte_t pte) { return pte_val(pte) & _PAGE_DIRTY; }
static inline int pte_young(pte_t pte) { return pte_val(pte) & _PAGE_ACCESSED; }
static inline int pte_file(pte_t pte) { return pte_val(pte) & _PAGE_FILE; }
static inline int pte_write(pte_t pte) { return pte_val(pte) & _PAGE_WRITE; }
static inline int pte_special(pte_t pte){ return 0; }
static inline pte_t pte_wrprotect(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_WRITE)); return pte; }
static inline pte_t pte_mkclean(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_DIRTY)); return pte; }
static inline pte_t pte_mkold(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_ACCESSED)); return pte; }
static inline pte_t pte_mkwrite(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_WRITE)); return pte; }
static inline pte_t pte_mkdirty(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_DIRTY)); return pte; }
static inline pte_t pte_mkyoung(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_ACCESSED)); return pte; }
static inline pte_t pte_mkhuge(pte_t pte) { set_pte(&pte, __pte(pte_val(pte) | _PAGE_SZHUGE)); return pte; }
static inline pte_t pte_mkspecial(pte_t pte) { return pte; }
/*
* Conversion functions: convert a page and protection to a page entry.
*
* extern pte_t mk_pte(struct page *page, pgprot_t pgprot)
*/
#define mk_pte(page,pgprot) \
({ \
pte_t __pte; \
\
set_pte(&__pte, __pte((((page)-mem_map) << PAGE_SHIFT) | \
__MEMORY_START | pgprot_val((pgprot)))); \
__pte; \
})
/*
* This takes a (absolute) physical page address that is used
* by the remapping functions
*/
#define mk_pte_phys(physpage, pgprot) \
({ pte_t __pte; set_pte(&__pte, __pte(physpage | pgprot_val(pgprot))); __pte; })
static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
{ set_pte(&pte, __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot))); return pte; }
/* Encode and decode a swap entry */
#define __swp_type(x) (((x).val & 3) + (((x).val >> 1) & 0x3c))
#define __swp_offset(x) ((x).val >> 8)
#define __swp_entry(type, offset) ((swp_entry_t) { ((offset << 8) + ((type & 0x3c) << 1) + (type & 3)) })
#define __pte_to_swp_entry(pte) ((swp_entry_t) { pte_val(pte) })
#define __swp_entry_to_pte(x) ((pte_t) { (x).val })
/* Encode and decode a nonlinear file mapping entry */
#define PTE_FILE_MAX_BITS 29
#define pte_to_pgoff(pte) (pte_val(pte))
#define pgoff_to_pte(off) ((pte_t) { (off) | _PAGE_FILE })
#endif /* !__ASSEMBLY__ */
#define pfn_pte(pfn, prot) __pte(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
#define pfn_pmd(pfn, prot) __pmd(((pfn) << PAGE_SHIFT) | pgprot_val(prot))
#endif /* __ASM_SH_PGTABLE_64_H */
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