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SubjectRe: [PATCH] x86: make mm/gup.c more virtualization friendly
No objections from me.

On Wed, Sep 17, 2008 at 04:48:17PM +0100, Jan Beulich wrote:
> Since pte_flags() is much cheaper than pte_val() in some virtualized
> environments (namely, Xen), use the former whereever possible.
>
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> Cc: Nick Piggin <npiggin@suse.de>
>
> ---
> arch/x86/mm/gup.c | 10 +++++-----
> include/asm-x86/pgtable.h | 2 +-
> 2 files changed, 6 insertions(+), 6 deletions(-)
>
> --- linux-2.6.27-rc6/arch/x86/mm/gup.c 2008-08-21 14:37:29.000000000 +0200
> +++ 2.6.27-rc6-x86-gup-virt/arch/x86/mm/gup.c 2008-09-02 13:33:42.000000000 +0200
> @@ -82,7 +82,7 @@ static noinline int gup_pte_range(pmd_t
> pte_t pte = gup_get_pte(ptep);
> struct page *page;
>
> - if ((pte_val(pte) & (mask | _PAGE_SPECIAL)) != mask) {
> + if ((pte_flags(pte) & (mask | _PAGE_SPECIAL)) != mask) {
> pte_unmap(ptep);
> return 0;
> }
> @@ -116,10 +116,10 @@ static noinline int gup_huge_pmd(pmd_t p
> mask = _PAGE_PRESENT|_PAGE_USER;
> if (write)
> mask |= _PAGE_RW;
> - if ((pte_val(pte) & mask) != mask)
> + if ((pte_flags(pte) & mask) != mask)
> return 0;
> /* hugepages are never "special" */
> - VM_BUG_ON(pte_val(pte) & _PAGE_SPECIAL);
> + VM_BUG_ON(pte_flags(pte) & _PAGE_SPECIAL);
> VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
>
> refs = 0;
> @@ -173,10 +173,10 @@ static noinline int gup_huge_pud(pud_t p
> mask = _PAGE_PRESENT|_PAGE_USER;
> if (write)
> mask |= _PAGE_RW;
> - if ((pte_val(pte) & mask) != mask)
> + if ((pte_flags(pte) & mask) != mask)
> return 0;
> /* hugepages are never "special" */
> - VM_BUG_ON(pte_val(pte) & _PAGE_SPECIAL);
> + VM_BUG_ON(pte_flags(pte) & _PAGE_SPECIAL);
> VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
>
> refs = 0;
> --- linux-2.6.27-rc6/include/asm-x86/pgtable.h 2008-08-21 14:37:34.000000000 +0200
> +++ 2.6.27-rc6-x86-gup-virt/include/asm-x86/pgtable.h 2008-09-02 13:31:50.000000000 +0200
> @@ -183,7 +183,7 @@ static inline int pte_exec(pte_t pte)
>
> static inline int pte_special(pte_t pte)
> {
> - return pte_val(pte) & _PAGE_SPECIAL;
> + return pte_flags(pte) & _PAGE_SPECIAL;
> }
>
> static inline int pmd_large(pmd_t pte)
>
>


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