Re: [Xen-devel] [PATCH 3/6] libxl: add backend type to vkb

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Oct 05, 2017 at 12:07:08PM +0300, Oleksandr Grytsov wrote:
> From: Oleksandr Grytsov <oleksandr_grytsov@xxxxxxxx>
> 
> New field backend_type is added to vkb device
> in order to have QEMU and user space backend
> simultaneously. Each vkb backend shall read
> appropriate XS entry and service only own
> frontends.
> 
> Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@xxxxxxxx>
> ---
>  tools/libxl/libxl_create.c  |  4 ++++
>  tools/libxl/libxl_dm.c      |  2 ++
>  tools/libxl/libxl_types.idl |  7 +++++++
>  tools/libxl/libxl_vkb.c     | 10 +++++++++-
>  tools/xl/xl_parse.c         |  4 ++++
>  5 files changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index f813114..7268f7f 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -1349,6 +1349,7 @@ static void domcreate_launch_dm(libxl__egc *egc, 
> libxl__multidev *multidev,
>          }
>  
>          libxl_device_vkb_init(&vkb);
> +        vkb.backend_type = LIBXL_VKB_BACKEND_QEMU;

Hmm... See below.

>          libxl__device_add(gc, domid, &libxl__vkb_devtype, &vkb);
>          libxl_device_vkb_dispose(&vkb);
>  
> @@ -1376,6 +1377,9 @@ static void domcreate_launch_dm(libxl__egc *egc, 
> libxl__multidev *multidev,
>          for (i = 0; i < d_config->num_vfbs; i++) {
>              libxl__device_add(gc, domid, &libxl__vfb_devtype,
>                                &d_config->vfbs[i]);
> +        }
> +
> +        for (i = 0; i < d_config->num_vkbs; i++) {
>              libxl__device_add(gc, domid, &libxl__vkb_devtype,
>                                &d_config->vkbs[i]);
>          }
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index 98f89a9..d8b0ee7 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -1728,6 +1728,8 @@ static int 
> libxl__vfb_and_vkb_from_hvm_guest_config(libxl__gc *gc,
>  
>      vkb->backend_domid = 0;
>      vkb->devid = 0;
> +    vkb->backend_type = LIBXL_VKB_BACKEND_QEMU;
> +
>      return 0;
>  }
>  
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index cd0c06f..65cd81a 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -240,6 +240,12 @@ libxl_checkpointed_stream = 
> Enumeration("checkpointed_stream", [
>      (2, "COLO"),
>      ])
>  
> +libxl_vkb_backend = Enumeration("vkb_backend", [
> +    (0, "UNKNOWN"),
> +    (1, "QEMU"),
> +    (2, "LINUX")
> +    ])

Originally this is only internal detail, but now you want to expose
this.  You need to set the default value for this; otherwise you could
break migration.

And then you also need to provide a setdefault function for
libxl_device_vkb.

Also I'm a bit confused because the LINUX type is not used in this
series.

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