Re: [Xen-devel] [PATCH] libxl: prefer qdisk for <driver name='file'>

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-06-20 at 15:07 -0600, Jim Fehlig wrote:
> The libxl driver currently sets the disk backend to
> LIBXL_DISK_BACKEND_TAP when <driver name='file'> is specified
> in the <disk> config.  qdisk should be prefered with this
> configuration, otherwise existing configuration such as the
> following, which worked with the old Xen driver, will not work
> with the libxl driver

OOI why not let libxl pick the most appropriate backend for (most of)
these alternatives?

> 
>   <disk type='file' device='cdrom'>
>     <driver name='file'/>
>     <source file='/path/to/some/iso'/>
>     <target dev='hdc' bus='ide'/>
>     <readonly/>
>   </disk>
> 
> In addition, tap performs poorly compared to qdisk.
> 
> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
> ---
>  src/libxl/libxl_conf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
> index fdbb522..4b6b5c0 100644
> --- a/src/libxl/libxl_conf.c
> +++ b/src/libxl/libxl_conf.c
> @@ -796,7 +796,7 @@ libxlMakeDisk(virDomainDiskDefPtr l_disk, 
> libxl_device_disk *x_disk)
>                  return -1;
>              }
>              x_disk->format = LIBXL_DISK_FORMAT_RAW;
> -            x_disk->backend = LIBXL_DISK_BACKEND_TAP;
> +            x_disk->backend = LIBXL_DISK_BACKEND_QDISK;
>          } else if (STREQ(driver, "phy")) {
>              if (format != VIR_STORAGE_FILE_NONE &&
>                  format != VIR_STORAGE_FILE_RAW) {



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