Re: [Xen-devel] [PATCH v1 01/12] libxl/hotplug: add support for getting domid

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 02/10/13 10:24, Roger Pau Monne wrote:
> This patch writes Dom0 domid on xenstore (like it's done for other
> guests), and adds a libxl helper function to fetch that domid from
> xenstore.
>
> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
> ---
>  tools/hotplug/Linux/init.d/xencommons |    1 +
>  tools/libxl/libxl.c                   |   17 +++++++++++++++++
>  tools/libxl/libxl_internal.h          |    3 +++
>  3 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/tools/hotplug/Linux/init.d/xencommons 
> b/tools/hotplug/Linux/init.d/xencommons
> index a2e633b..43e09bc 100644
> --- a/tools/hotplug/Linux/init.d/xencommons
> +++ b/tools/hotplug/Linux/init.d/xencommons
> @@ -110,6 +110,7 @@ do_start () {
>  
>               echo Setting domain 0 name...
>               ${BINDIR}/xenstore-write "/local/domain/0/name" "Domain-0"
> +             ${BINDIR}/xenstore-write "/local/domain/0/domid" "0"
>       fi
>  
>       echo Starting xenconsoled...
> diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
> index 1bce4bb..5417b48 100644
> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c
> @@ -1688,6 +1688,23 @@ int libxl_vncviewer_exec(libxl_ctx *ctx, uint32_t 
> domid, int autopass)
>      return ERROR_FAIL;
>  }
>  
> +int libxl__get_domid(libxl__gc *gc, uint32_t *domid)
> +{
> +    int rc;
> +    const char *xs_domid;
> +
> +    rc = libxl__xs_read_checked(gc, XBT_NULL, DOMID_XS_PATH, &xs_domid);
> +    if (rc || !xs_domid) {

NULL domid check should be done before xenstore read, as an xs read is
quite a long operation.

> +        rc = rc ? rc : ERROR_FAIL;
> +        goto out;
> +    }
> +
> +    *domid = atoi(xs_domid);

atoi() lacks any error reporting.  Use strtoul() and perhaps even a
sanity check on the return value against the valid bounds for a domid.

~Andrew

> +
> +out:
> +    return rc;
> +}
> +
>  
> /******************************************************************************/
>  
>  /* generic callback for devices that only need to set ao_complete */
> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
> index f051d91..3b74726 100644
> --- a/tools/libxl/libxl_internal.h
> +++ b/tools/libxl/libxl_internal.h
> @@ -101,6 +101,7 @@
>  #define STUBDOM_SPECIAL_CONSOLES 3
>  #define TAP_DEVICE_SUFFIX "-emu"
>  #define DISABLE_UDEV_PATH "libxl/disable_udev"
> +#define DOMID_XS_PATH "domid"
>  
>  #define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
>  
> @@ -978,6 +979,8 @@ _hidden const char *libxl__device_nic_devname(libxl__gc 
> *gc,
>                                                uint32_t devid,
>                                                libxl_nic_type type);
>  
> +_hidden int libxl__get_domid(libxl__gc *gc, uint32_t *domid);
> +
>  /*
>   * libxl__ev_devstate - waits a given time for a device to
>   * reach a given state.  Follows the libxl_ev_* conventions.


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