linux-kernel - Re: [patch 6/7] powerpc: implement pte

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Date:	Fri, 06 Jun 2008 14:04:53 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	npiggin@...e.de
Cc:	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, paulus@...ba.org
Subject: Re: [patch 6/7] powerpc: implement pte_special

On Thu, 2008-06-05 at 19:43 +1000, npiggin@...e.de wrote:
> plain text document attachment (powerpc-implement-pte_special.patch)
> Implement PTE_SPECIAL for powerpc. At the moment I only have a spare bit for
> the 4k pages config, but Ben has freed up another one for 64k pages that I
> can use, so this patch should include that before it goes upstream.
> 
> Signed-off-by: Nick Piggin <npiggin@...e.de>

Ack that bit. _PAGE_SPECIAL will replace _PAGE_HASHPTE on 64K (ie.
0x400). The patch that frees that bit should get into powerpc.git (and
from there -mm) as soon as paulus catches up with his backlog :-)

Cheers,
Ben.

> ---
> Index: linux-2.6/include/asm-powerpc/pgtable-ppc64.h
> ===================================================================
> --- linux-2.6.orig/include/asm-powerpc/pgtable-ppc64.h
> +++ linux-2.6/include/asm-powerpc/pgtable-ppc64.h
> @@ -239,7 +239,7 @@ static inline int pte_write(pte_t pte) {
>  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_special(pte_t pte) { return 0; }
> +static inline int pte_special(pte_t pte) { return pte_val(pte) & _PAGE_SPECIAL; }
>  
>  static inline void pte_uncache(pte_t pte) { pte_val(pte) |= _PAGE_NO_CACHE; }
>  static inline void pte_cache(pte_t pte)   { pte_val(pte) &= ~_PAGE_NO_CACHE; }
> @@ -259,7 +259,7 @@ static inline pte_t pte_mkyoung(pte_t pt
>  static inline pte_t pte_mkhuge(pte_t pte) {
>  	return pte; }
>  static inline pte_t pte_mkspecial(pte_t pte) {
> -	return pte; }
> +	pte_val(pte) |= _PAGE_SPECIAL; return pte; }
>  
>  /* Atomic PTE updates */
>  static inline unsigned long pte_update(struct mm_struct *mm,
> Index: linux-2.6/include/asm-powerpc/pgtable-4k.h
> ===================================================================
> --- linux-2.6.orig/include/asm-powerpc/pgtable-4k.h
> +++ linux-2.6/include/asm-powerpc/pgtable-4k.h
> @@ -45,6 +45,8 @@
>  #define _PAGE_GROUP_IX  0x7000 /* software: HPTE index within group */
>  #define _PAGE_F_SECOND  _PAGE_SECONDARY
>  #define _PAGE_F_GIX     _PAGE_GROUP_IX
> +#define _PAGE_SPECIAL	0x10000 /* software: special page */
> +#define __HAVE_ARCH_PTE_SPECIAL
>  
>  /* PTE flags to conserve for HPTE identification */
>  #define _PAGE_HPTEFLAGS (_PAGE_BUSY | _PAGE_HASHPTE | \
> Index: linux-2.6/include/asm-powerpc/pgtable-64k.h
> ===================================================================
> --- linux-2.6.orig/include/asm-powerpc/pgtable-64k.h
> +++ linux-2.6/include/asm-powerpc/pgtable-64k.h
> @@ -74,6 +74,7 @@ static inline struct subpage_prot_table 
>  #define _PAGE_HPTE_SUB0	0x08000000 /* combo only: first sub page */
>  #define _PAGE_COMBO	0x10000000 /* this is a combo 4k page */
>  #define _PAGE_4K_PFN	0x20000000 /* PFN is for a single 4k page */
> +#define _PAGE_SPECIAL	0x0	   /* don't have enough room for this yet */
>  
>  /* Note the full page bits must be in the same location as for normal
>   * 4k pages as the same asssembly will be used to insert 64K pages
> 

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