On Fri, Jul 16, 2010 at 10:13:14AM +0800, Lai Jiangshan wrote:
>
> a light weight version of get_user_page_and_protection()
>
> Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
> ---
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index a34c785..d0e4f2f 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -618,6 +618,8 @@ static inline void clone_pgd_range(pgd_t *dst, pgd_t *src, int count)
> memcpy(dst, src, count * sizeof(pgd_t));
> }
>
> +extern
> +struct page *get_user_page_and_protection(unsigned long addr, int *writable);
>
> #include <asm-generic/pgtable.h>
> #endif /* __ASSEMBLY__ */
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 6382140..de44847 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1832,23 +1832,6 @@ static void kvm_unsync_pages(struct kvm_vcpu *vcpu, gfn_t gfn)
> }
> }
>
> -/* get a current mapped page fast, and test whether the page is writable. */
> -static struct page *get_user_page_and_protection(unsigned long addr,
> - int *writable)
> -{
> - struct page *page[1];
> -
> - if (__get_user_pages_fast(addr, 1, 1, page) == 1) {
> - *writable = 1;
> - return page[0];
> - }
> - if (__get_user_pages_fast(addr, 1, 0, page) == 1) {
> - *writable = 0;
> - return page[0];
> - }
> - return NULL;
> -}
> -
> static pfn_t kvm_get_pfn_for_page_fault(struct kvm *kvm, gfn_t gfn,
> int write_fault, int *host_writable)
> {
> diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
> index a4ce19f..34b05c7 100644
> --- a/arch/x86/mm/gup.c
> +++ b/arch/x86/mm/gup.c
> @@ -275,7 +275,6 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write,
>
> return nr;
> }
> -EXPORT_SYMBOL_GPL(__get_user_pages_fast);
>
> /**
> * get_user_pages_fast() - pin user pages in memory
> @@ -375,3 +374,83 @@ slow_irqon:
> return ret;
> }
> }
> +
> +/*
> + * get a current mapped page fast, and test whether the page is writable.
> + * equivalent version(but slower):
> + * {
> + * struct page *page[1];
> + *
> + * if (__get_user_pages_fast(addr, 1, 1, page) == 1) {
> + * *writable = 1;
> + * return page[0];
> + * }
> + * if (__get_user_pages_fast(addr, 1, 0, page) == 1) {
> + * *writable = 0;
> + * return page[0];
> + * }
> + * return NULL;
> + * }
> + */
> +struct page *get_user_page_and_protection(unsigned long addr, int *writable)
> +{
> + unsigned long flags;
> + struct mm_struct *mm = current->mm;
> + pgd_t *pgdp;
> + pud_t *pudp;
> + pmd_t *pmdp;
> + pte_t pte, *ptep;
> +
> + unsigned long mask = _PAGE_PRESENT | _PAGE_USER;
> + unsigned long offset = 0;
> + struct page *head, *page = NULL;
> +
> + addr &= PAGE_MASK;
> +
> + local_irq_save(flags);
> + pgdp = pgd_offset(mm, addr);
> + if (!pgd_present(*pgdp))
> + goto out;
Better introduce __get_user_pages_ptes_fast, and share code with
__get_user_pages_fast (except _ptes_fast copies the pte values to
pte_t array).
--
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