Re: [Xen-devel] [RFC XEN PATCH 14/16] tools/libxl: add support to map files on pmem devices to guests

[Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx>]

On Mon, Oct 10, 2016 at 08:32:33AM +0800, Haozhong Zhang wrote:
> We can map host pmem devices or files on pmem devices to guests. This
> patch adds support to map files on pmem devices. The implementation
> relies on the Linux pmem driver and kernel APIs, so it currently

May want to mention which CONFIG_ options are needed.
> functions only when libxl is compiled for Linux.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> ---
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> ---
>  tools/libxl/libxl_nvdimm.c | 73 
> +++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 72 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libxl/libxl_nvdimm.c b/tools/libxl/libxl_nvdimm.c
> index 7bcbaaf..b3ba19a 100644
> --- a/tools/libxl/libxl_nvdimm.c
> +++ b/tools/libxl/libxl_nvdimm.c
> @@ -25,6 +25,9 @@
>  #include <unistd.h>
>  #include <errno.h>
>  #include <stdint.h>
> +#include <sys/ioctl.h>
> +#include <linux/fs.h>
> +#include <linux/fiemap.h>
>  
>  #include "libxl_internal.h"
>  #include "libxl_arch.h"
> @@ -97,10 +100,78 @@ static int add_pages(libxl__gc *gc, uint32_t domid,
>      return ret;
>  }
>  
> +static uint64_t
> +get_file_extents(libxl__gc *gc, int fd, unsigned long length,
> +                 struct fiemap_extent **extents_r)
> +{
> +    struct fiemap *fiemap;
> +    uint64_t nr_extents = 0, extents_size;
> +
> +    fiemap = libxl__zalloc(gc, sizeof(*fiemap));
> +    if ( !fiemap )
> +        goto out;
> +
> +    fiemap->fm_length = length;
> +    if ( ioctl(fd, FS_IOC_FIEMAP, fiemap) < 0 )
> +        goto out;
> +
> +    nr_extents = fiemap->fm_mapped_extents;
> +    extents_size = sizeof(struct fiemap_extent) * nr_extents;
> +    fiemap = libxl__realloc(gc, fiemap, sizeof(*fiemap) + extents_size);
> +    if ( !fiemap )
> +        goto out;
> +
> +    memset(fiemap->fm_extents, 0, extents_size);
> +    fiemap->fm_extent_count = nr_extents;
> +    fiemap->fm_mapped_extents = 0;
> +
> +    if ( ioctl(fd, FS_IOC_FIEMAP, fiemap) < 0 )
> +        goto out;
> +
> +    *extents_r = fiemap->fm_extents;
> +
> + out:
> +    return nr_extents;
> +}
> +
>  static int add_file(libxl__gc *gc, uint32_t domid, int fd,
>                      xen_pfn_t mfn, xen_pfn_t gpfn, unsigned long nr_mfns)
>  {
> -    return -EINVAL;
> +    struct fiemap_extent *extents;
> +    uint64_t nr_extents, i;
> +    int ret = 0;
> +
> +    nr_extents = get_file_extents(gc, fd, nr_mfns << XC_PAGE_SHIFT, 
> &extents);
> +    if ( !nr_extents )
> +        return -EIO;
> +
> +    for ( i = 0; i < nr_extents; i++ )
> +    {
> +        uint64_t p_offset = extents[i].fe_physical;
> +        uint64_t l_offset = extents[i].fe_logical;
> +        uint64_t length = extents[i].fe_length;
> +
> +        if ( extents[i].fe_flags & ~FIEMAP_EXTENT_LAST )
> +        {
> +            ret = -EINVAL;
> +            break;
> +        }
> +
> +        if ( (p_offset | l_offset | length) & ~XC_PAGE_MASK )
> +        {
> +            ret = -EINVAL;
> +            break;
> +        }
> +
> +        ret = add_pages(gc, domid,
> +                        mfn + (p_offset >> XC_PAGE_SHIFT),
> +                        gpfn + (l_offset >> XC_PAGE_SHIFT),
> +                        length >> XC_PAGE_SHIFT);
> +        if ( ret )
> +            break;
> +    }
> +
> +    return ret;
>  }
>  
>  int libxl_nvdimm_add_device(libxl__gc *gc,
> -- 
> 2.10.1
> 
> 
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