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    Subject[patch 01/28]xen: Allocate and free vmalloc areas
    Allocate/destroy a 'vmalloc' VM area: alloc_vm_area and free_vm_area
    The alloc function ensures that page tables are constructed for the
    region of kernel virtual address space and mapped into init_mm.

    Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
    Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
    Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
    Signed-off-by: Chris Wright <chrisw@sous-sol.org>
    Cc: "Jan Beulich" <JBeulich@novell.com>
    Cc: "Andi Kleen" <ak@muc.de>

    ---
    include/linux/vmalloc.h | 4 +++
    mm/vmalloc.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 57 insertions(+)

    ===================================================================
    --- a/include/linux/vmalloc.h
    +++ b/include/linux/vmalloc.h
    @@ -69,6 +69,10 @@ extern int map_vm_area(struct vm_struct
    struct page ***pages);
    extern void unmap_vm_area(struct vm_struct *area);

    +/* Allocate/destroy a 'vmalloc' VM area. */
    +extern struct vm_struct *alloc_vm_area(unsigned long size);
    +extern void free_vm_area(struct vm_struct *area);
    +
    /*
    * Internals. Dont't use..
    */
    ===================================================================
    --- a/mm/vmalloc.c
    +++ b/mm/vmalloc.c
    @@ -762,3 +762,56 @@ void __attribute__((weak)) vmalloc_sync
    void __attribute__((weak)) vmalloc_sync_all(void)
    {
    }
    +
    +
    +static int f(pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
    +{
    + /* apply_to_page_range() does all the hard work. */
    + return 0;
    +}
    +
    +/**
    + * alloc_vm_area - allocate a range of kernel address space
    + * @size: size of the area
    + * @returns: NULL on failure, vm_struct on success
    + *
    + * This function reserves a range of kernel address space, and
    + * allocates pagetables to map that range. No actual mappings
    + * are created. If the kernel address space is not shared
    + * between processes, it syncs the pagetable across all
    + * processes.
    + */
    +struct vm_struct *alloc_vm_area(unsigned long size)
    +{
    + struct vm_struct *area;
    +
    + area = get_vm_area(size, VM_IOREMAP);
    + if (area == NULL)
    + return NULL;
    +
    + /*
    + * This ensures that page tables are constructed for this region
    + * of kernel virtual address space and mapped into init_mm.
    + */
    + if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
    + area->size, f, NULL)) {
    + free_vm_area(area);
    + return NULL;
    + }
    +
    + /* Make sure the pagetables are constructed in process kernel
    + mappings */
    + vmalloc_sync_all();
    +
    + return area;
    +}
    +EXPORT_SYMBOL_GPL(alloc_vm_area);
    +
    +void free_vm_area(struct vm_struct *area)
    +{
    + struct vm_struct *ret;
    + ret = remove_vm_area(area->addr);
    + BUG_ON(ret != area);
    + kfree(area);
    +}
    +EXPORT_SYMBOL_GPL(free_vm_area);
    --

    -
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