Re: [Xen-devel] [PATCHv4 14/14] xen/gntdev: provide find_special_page VMA operation

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 26 Jan 2015, David Vrabel wrote:
> For a PV guest, use the find_special_page op to find the right page.
> To handle VMAs being split, remember the start of the original VMA so
> the correct index in the pages array can be calculated.
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>

Very nice.

Reviewed-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>


>  drivers/xen/gntdev.c |   12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 8ea10eb..826e731 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -93,6 +93,7 @@ struct grant_map {
>       struct gnttab_map_grant_ref   *kmap_ops;
>       struct gnttab_unmap_grant_ref *kunmap_ops;
>       struct page **pages;
> +     unsigned long pages_vm_start;
>  };
>  
>  static int unmap_grant_pages(struct grant_map *map, int offset, int pages);
> @@ -444,9 +445,18 @@ static void gntdev_vma_close(struct vm_area_struct *vma)
>       gntdev_put_map(priv, map);
>  }
>  
> +static struct page *gntdev_vma_find_special_page(struct vm_area_struct *vma,
> +                                              unsigned long addr)
> +{
> +     struct grant_map *map = vma->vm_private_data;
> +
> +     return map->pages[(addr - map->pages_vm_start) >> PAGE_SHIFT];
> +}
> +
>  static struct vm_operations_struct gntdev_vmops = {
>       .open = gntdev_vma_open,
>       .close = gntdev_vma_close,
> +     .find_special_page = gntdev_vma_find_special_page,
>  };
>  
>  /* ------------------------------------------------------------------ */
> @@ -870,6 +880,8 @@ static int gntdev_mmap(struct file *flip, struct 
> vm_area_struct *vma)
>                                           vma->vm_end - vma->vm_start,
>                                           set_grant_ptes_as_special, NULL);
>               }
> +
> +             map->pages_vm_start = vma->vm_start;
>       }
>  
>       return 0;
> -- 
> 1.7.10.4
> 
> 
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> 

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