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

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 01/27/17 17:10 -0500, Konrad Rzeszutek Wilk wrote:
> 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.
I'll drop the support to map a file. After consulting our driver
developers, there is really no stable way to fix mappings between the
file extents and their physical locations, so the fiemap code in this
patch in fact may not work correctly.

Thanks,
Haozhong


> > 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
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > https://lists.xen.org/xen-devel
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