Re: [Xen-devel] [PATCH 1/3] libxl: make libxl__need_xenpv_qemu() operate on domain config

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

On Thu, Mar 10, 2016 at 3:00 PM, Juergen Gross <jgross@xxxxxxxx> wrote:
> libxl__need_xenpv_qemu() is called with configuration data for console,
> vfbs, disks and channels today in order to evaluate the need for
> starting a device model for a pv domain.
>
> The console data is local to the caller and setup in a way to never
> require a device model. All other data is taken from the domain config
> structure.
>
> In order to support other device backends via qemu change the interface
> of libxl__need_xenpv_qemu() to take the domain config structure as
> input instead of the single device arrays.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
>  tools/libxl/libxl_create.c   |  9 +------
>  tools/libxl/libxl_dm.c       | 59 
> ++++++++++++--------------------------------
>  tools/libxl/libxl_internal.h |  5 +---
>  3 files changed, 18 insertions(+), 55 deletions(-)
>
> diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
> index 61b5c01..0e2b0a0 100644
> --- a/tools/libxl/libxl_create.c
> +++ b/tools/libxl/libxl_create.c
> @@ -1304,7 +1304,6 @@ static void domcreate_launch_dm(libxl__egc *egc, 
> libxl__multidev *multidev,
>      }
>      case LIBXL_DOMAIN_TYPE_PV:
>      {
> -        int need_qemu = 0;
>          libxl__device_console console;
>          libxl__device device;
>
> @@ -1314,17 +1313,11 @@ static void domcreate_launch_dm(libxl__egc *egc, 
> libxl__multidev *multidev,
>          }
>
>          init_console_info(gc, &console, 0);
> -
> -        need_qemu = libxl__need_xenpv_qemu(gc, 1, &console,
> -                d_config->num_vfbs, d_config->vfbs,
> -                d_config->num_disks, &d_config->disks[0],
> -                d_config->num_channels, &d_config->channels[0]);
> -
>          console.backend_domid = state->console_domid;
>          libxl__device_console_add(gc, domid, &console, state, &device);
>          libxl__device_console_dispose(&console);
>
> -        if (need_qemu) {
> +        if (libxl__need_xenpv_qemu(gc, d_config)) {
>              dcs->dmss.dm.guest_domid = domid;
>              libxl__spawn_local_dm(egc, &dcs->dmss.dm);
>              return;
> diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
> index 4aca38e..4b840f4 100644
> --- a/tools/libxl/libxl_dm.c
> +++ b/tools/libxl/libxl_dm.c
> @@ -2107,61 +2107,34 @@ int libxl__destroy_device_model(libxl__gc *gc, 
> uint32_t domid)
>                  GCSPRINTF("/local/domain/%d/image/device-model-pid", domid));
>  }
>
> -int libxl__need_xenpv_qemu(libxl__gc *gc,
> -        int nr_consoles, libxl__device_console *consoles,
> -        int nr_vfbs, libxl_device_vfb *vfbs,
> -        int nr_disks, libxl_device_disk *disks,
> -        int nr_channels, libxl_device_channel *channels)
> +int libxl__need_xenpv_qemu(libxl__gc *gc, libxl_domain_config *d_config)
>  {
> -    int i, ret = 0;
> +    int i, ret;
>      uint32_t domid;
>
> -    /*
> -     * qemu is required in order to support 2 or more consoles. So switch all
> -     * backends to qemu if this is the case
> -     */
> -    if (nr_consoles > 1) {
> -        for (i = 0; i < nr_consoles; i++)
> -            consoles[i].consback = LIBXL__CONSOLE_BACKEND_IOEMU;
> +    ret = libxl__get_domid(gc, &domid);
> +    if (ret) goto out;

Doesn't this mean that if libxl__get_domid() fails,
libxl__need_xenpv_qemu() will effectively return "true"?

I realize this is a bug in the existing code but there's no need to be
bug-for-bug compatible here. :-)

Maybe add an 'rc' variable, and make this:

rc = libxl__get_domid();
if(rc) goto out;

Other than that, looks good to me.

 -George

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