On 24/10/2016 11:57, Lorenzo Stoakes wrote:
> This patch unexports the low-level __get_user_pages() function. Recent
> refactoring of the get_user_pages* functions allow flags to be passed through
> get_user_pages() which eliminates the need for access to this function from its
> one user, kvm.
>
> We can see that the 2 calls to get_user_pages() which replace __get_user_pages()
> in kvm_main.c are equivalent by examining their call stacks:
>
> get_user_page_nowait():
> get_user_pages(start, 1, flags, page, NULL)
> __get_user_pages_locked(current, current->mm, start, 1, page, NULL, NULL,
> false, flags | FOLL_TOUCH)
> __get_user_pages(current, current->mm, start, 1,
> flags | FOLL_TOUCH | FOLL_GET, page, NULL, NULL)
>
> check_user_page_hwpoison():
> get_user_pages(addr, 1, flags, NULL, NULL)
> __get_user_pages_locked(current, current->mm, addr, 1, NULL, NULL, NULL,
> false, flags | FOLL_TOUCH)
> __get_user_pages(current, current->mm, addr, 1, flags | FOLL_TOUCH, NULL,
> NULL, NULL)
>
> Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
> ---
> include/linux/mm.h | 4 ----
> mm/gup.c | 3 +--
> mm/nommu.c | 2 +-
> virt/kvm/kvm_main.c | 10 ++++------
> 4 files changed, 6 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 3a19185..a92c8d7 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1271,10 +1271,6 @@ extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *
> extern int access_remote_vm(struct mm_struct *mm, unsigned long addr,
> void *buf, int len, unsigned int gup_flags);
>
> -long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> - unsigned long start, unsigned long nr_pages,
> - unsigned int foll_flags, struct page **pages,
> - struct vm_area_struct **vmas, int *nonblocking);
> long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm,
> unsigned long start, unsigned long nr_pages,
> unsigned int gup_flags, struct page **pages,
> diff --git a/mm/gup.c b/mm/gup.c
> index 7aa113c..ec4f827 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -526,7 +526,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags)
> * instead of __get_user_pages. __get_user_pages should be used only if
> * you need some special @gup_flags.
> */
> -long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> +static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> unsigned long start, unsigned long nr_pages,
> unsigned int gup_flags, struct page **pages,
> struct vm_area_struct **vmas, int *nonblocking)
> @@ -631,7 +631,6 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> } while (nr_pages);
> return i;
> }
> -EXPORT_SYMBOL(__get_user_pages);
>
> bool vma_permits_fault(struct vm_area_struct *vma, unsigned int fault_flags)
> {
> diff --git a/mm/nommu.c b/mm/nommu.c
> index db5fd17..8b8faaf 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -109,7 +109,7 @@ unsigned int kobjsize(const void *objp)
> return PAGE_SIZE << compound_order(page);
> }
>
> -long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> +static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> unsigned long start, unsigned long nr_pages,
> unsigned int foll_flags, struct page **pages,
> struct vm_area_struct **vmas, int *nonblocking)
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 28510e7..2907b7b 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1346,21 +1346,19 @@ unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *w
> static int get_user_page_nowait(unsigned long start, int write,
> struct page **page)
> {
> - int flags = FOLL_TOUCH | FOLL_NOWAIT | FOLL_HWPOISON | FOLL_GET;
> + int flags = FOLL_NOWAIT | FOLL_HWPOISON;
>
> if (write)
> flags |= FOLL_WRITE;
>
> - return __get_user_pages(current, current->mm, start, 1, flags, page,
> - NULL, NULL);
> + return get_user_pages(start, 1, flags, page, NULL);
> }
>
> static inline int check_user_page_hwpoison(unsigned long addr)
> {
> - int rc, flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_WRITE;
> + int rc, flags = FOLL_HWPOISON | FOLL_WRITE;
>
> - rc = __get_user_pages(current, current->mm, addr, 1,
> - flags, NULL, NULL, NULL);
> + rc = get_user_pages(addr, 1, flags, NULL, NULL);
> return rc == -EHWPOISON;
> }
>
>
Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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