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Re: [Xen-devel] [PATCH v4 1/2] libxl: postpone backend name resolution
On 04/15/2013 10:55 AM, Roger Pau Monné wrote:
On 12/04/13 17:22, Daniel De Graaf wrote:
This adds a backend_domname field in libxl devices that contain a
backend_domid field, allowing either a domid or a domain name to be
specified in the configuration structures. The domain name is resolved
into a domain ID in the _setdefault function when adding the device.
This change allows the backend of the block devices to be specified
(which previously required passing the libxl_ctx down into the block
device parser), and will simplify specification of backend domains in
other users of libxl.
Signed-off-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
This patch does not include the changes to tools/libxl/libxlu_disk_l.c
and tools/libxl/libxlu_disk_l.h because the diffs contain unrelated
changes due to different generator versions.
Changes since v3:
- Add #define LIBXL_HAVE_DEVICE_BACKEND_DOMNAME in libxl.h
- Create libxl_domain_qualifier_to_domid function in libxl_util.h
docs/misc/xl-disk-configuration.txt | 12 ++++++
tools/libxl/libxl.c | 17 +++++++--
tools/libxl/libxl.h | 12 ++++++
tools/libxl/libxl_types.idl | 5 +++
tools/libxl/libxl_utils.c | 19 ++++++++++
tools/libxl/libxl_utils.h | 1 +
tools/libxl/libxlu_disk_l.l | 1 +
tools/libxl/xl_cmdimpl.c | 75 ++++++++-----------------------------
8 files changed, 78 insertions(+), 64 deletions(-)
diff --git a/docs/misc/xl-disk-configuration.txt
b/docs/misc/xl-disk-configuration.txt
index 86c16be..5bd456d 100644
--- a/docs/misc/xl-disk-configuration.txt
+++ b/docs/misc/xl-disk-configuration.txt
@@ -139,6 +139,18 @@ cdrom
Convenience alias for "devtype=cdrom".
+backend=<domain-name>
+---------------------
+
+Description: Designates a backend domain for the device
+Supported values: Valid domain names
+Mandatory: No
+
+Specifies the backend domain which this device should attach to. This
+defaults to domain 0. Specifying another domain requires setting up a
+driver domain which is outside the scope of this document.
+
+
backendtype=<backend-type>
--------------------------
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 572c2c6..b994fea 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1730,13 +1730,21 @@ static int libxl__device_nextid(libxl__gc *gc, uint32_t
domid, char *device)
return nextid;
}
+static int libxl__resolve_domid(libxl__gc *gc, const char *name,
+ uint32_t *domid)
+{
+ if (!name)
+ return 0;
This is just my opinion, but I find this function ambiguous, it will
return 0 (success), if either name is NULL, or name != NULL and it can
be resolved to a domid, which means that even when returning 0 the value
in *domid might be uninitialized (if name == NULL). I would rather do
something like
if (!name || !domid)
return ERROR_INVAL;
And make sure callers only call this function if there's a real need to
resolve a domid.
This is an internal function which is called only when there is a real need
to resolve a domid. The value of domid is never uninitialized when calling
this function; it is always the value of backend_domid, and retains that
value when backend_domname is not specified.
Also, do we check somewhere that both backend_domid and backend_domname
are not specified at the same time?
Since backend_domid is an integer that defaults to 0 (which is a valid ID),
it's impossible to tell if the 0 was specified or if it was simply the
default. This is resolved by having backend_domname take precedence over
backend_domid when it is present.
--
Daniel De Graaf
National Security Agency
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