March 2006 - Devel - libvirt List Archives

[Libvir] Perl API for using libvirt
by Daniel P. Berrange 26 Apr '06

26 Apr '06

Hi Folks, I had a couple of hours spare, so I put together a set of Perl bindings for libvirt. I'm currently calling the module Sys::Virt which seems to be the most appropriate location in the CPAN namespace, but I'm open to suggestions if people think that sucks. I've currently got near 100% coverage of the C APIs, but not exposed all the static constants yet. There are a couple of trivial example programs illustrating use of the API for extracting info about domains.=20 For now you can grab a snapshot of the source for the binding using=20 Mercurial from the URL: http://hg.berrange.com/libraries/sys-virt When I've tested it more completely I'll upload it to CPAN Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] Request for additional entry points
by Jim Fehlig 13 Apr '06

13 Apr '06

As discussed on the xen-cim call on 3/31, the Xen CIM provider needs some additional entry points in libvirt. I would like to open a discussion about adding the following entry points to libvirt. virDomainSetConfig(virConnectPtr conn, const char *xmlDesc) Stores the domU config data in xenstore. The domU is not running yet but enumerating domains would return the config for the domain as well as any running domains. This would support the notion of a defined but inactive virtual machine. Daniel noted that the config could be cached in libvirt, preventing (to some degree) modifying the config out-of-band prior to activating the domain. Note that the current virConnectListDomains() implies enumerating only running domains since a list of domain IDs is returned. Perhaps virConnectListDomains() will have to be expanded to include defined domains or another entry point to enumerate defined domains. Related would be activating a defined domain. Would clients get the domain config (via virDomainGetXMLDesc()) and subsequently pass it to virDomainCreateLinux() or another entry point to create a defined domain? virDomainDeleteConfig(virConnectPtr conn, const char *name) Removed domU config from xenstore (or cache). DomU no longer "exists". What if domain is active upon invocation? virDomainSetCurrentMemory(virDomainPtr domain, unsigned long memory) Adjust the current memory usage for a domain. virDomainReboot(virDomainPtr domain) Reboot the domain. virDomainMigrate(virDomainPtr domain, const char *host) ?? Not sure what can of worms might be opened by this one :-). Thoughts? BTW, I can certainly help with the effort if an agreement is reached on adding this functionality. Regards, Jim

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[Libvir] autogen.sh error
by Ronald Aigner 10 Apr '06

10 Apr '06

Hi all, I downloaded libvirt from CVS and tried to run autogen.sh which stops with the following error message: configure: error: Xen store library not found What else do I need? How do I implement support for another hypervisor? Where do I have to turn which screws? Thanks, Ron.

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[Libvir] Patch to make reading of HTTP response more efficient
by Daniel P. Berrange 30 Mar '06

30 Mar '06

When processing the header of HTTP responses from Xend, libvirt currently reads data a single byte at a time. Since its using lowlevel UNIX read() function there is no buffering, which results in a large number of system calls. The attached patch re-factors the code so that it reads data in 4k chunks whenever possible. Since most rsponses are < 4k in size processing the response now only takes two read() syscalls, rather than several hundred. Of course most (90%) of the CPU overhead is still on the Xend/XenStored end of the channel, but that's out of our control until the XML-RPC API comes along. Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] unchecked `malloc' calls
by Jim Meyering 30 Mar '06

30 Mar '06

Hello, In browsing through the code, I noticed that there are many places in which the code doesn't check for malloc returning NULL. E.g., ./virsh.c: ids = malloc(sizeof(int) * maxid); ./virsh.c- virConnectListDomains(ctl->conn, &ids[0], maxid); ./virsh.c: *res = malloc(sz + 1); ./virsh.c- memcpy(*res, tkstr, sz); ./virsh.c: res = malloc(strlen(name) + 3); ./virsh.c- sprintf(res, "--%s", name); ./xmlrpc.c: buf = malloc(sizeof(*buf)); ./xmlrpc.c- buf->size = 1024; ./xmlrpc.c: xmlRpcValueDictElementPtr ret = malloc(sizeof(*ret)); ./xmlrpc.c- xmlNodePtr cur; ./xmlrpc.c- ./xmlrpc.c- memset(ret, 0, sizeof(*ret)); At first, seeing so many, I thought there must be a wrapper that handles the case of a NULL return value. But there are many places where the code *does* check for NULL. This may be a clue. Maybe it's planned... ./libvirt.c: * TODO: ... ./libvirt.c: * - memory wrappers for malloc/free ? Jim

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[Libvir] RFC: requesting APIs for host physical resource discovery
by Daniel P. Berrange 29 Mar '06

29 Mar '06

The current libvirt APIs allow the host's physical resources to be split up and allocated to guest domains, however, there is no way to discover what the available host resources actually are. Thus I would like to suggest the inclusion of new APIs to enable host resource discovery. As a starting point I'd like to be able to query the following information: * Number of physical CPUs - ability to enumerate the CPUs in the host, both those currently present, and theoretical maximum (to take account of hotplug). * Amount of RAM - actual physical RAM present, and that available for guest usage (eg discounting that reserved by a hypervisor or equiv) * CPU relationship - ie ability to distinguish between CPUs which are hyperthread siblings, on same core, or on separate sockets Alonside these basic queries it would be desirable to add a further resource resource management API to allow for setting of a guest domain's CPU affinity. ie ability control what CPUs the VMM is allowed to schedule a domain on. Once this first basic set of caapbilties for resource discovery are provided for, then I believe it will be neccessary to provide some more advanced queries, in particular: * NUMA topology - ability to enumerate NUMA nodes, the CPUs associated with each node & the RAM range mapped to that node Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] python/libvir.html example needs adjustment
by Jim Meyering 28 Mar '06

28 Mar '06

Hello, Trying a variant of this example from python/libvir.html: import libvirt import sys conn = libvirt.openReadOnly(None) if conn == None: print 'Failed to open connection to the hypervisor' sys.exit(1) dom0 = conn.lookupByName("Domain-0") if dom0 == None: print 'Failed to find the main domain' sys.exit(1) print "Domain 0: id %d running %s" % (dom0.ID(), dom0.OSType()) print dom0.info() I found that conn.lookupByName throws an exception when the specified name is not found. If the example is just out of date, it should use try:/except: instead of comparing dom0 to None, shouldn't it? You can demonstrate it like this: $ python -c 'import libvirt; libvirt.openReadOnly(None).lookupByName("x")' libvir: Xen Daemon error : GET operation failed: No such domain x Traceback (most recent call last): File "<string>", line 1, in ? File "/usr/lib/python2.4/site-packages/libvirt.py", line 213, in lookupByName if ret is None:raise libvirtError('virDomainLookupByName() failed') libvirt.libvirtError: virDomainLookupByName() failed [Exit 1] Jim

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[Libvir] use gcc's printf __attribute__
by Jim Meyering 27 Mar '06

27 Mar '06

Hello, I noticed that there are a few printf-like functions here, but that they don't benefit from gcc's format-string vs. arg-type checking. Here's a patch to enable that: However, to make it portable to non-gcc systems, this block of cpp directives needs to go somewhere (maybe libvirt.h?) so it'll be used from both files. #ifndef __attribute__ /* This feature is available in gcc versions 2.5 and later. */ # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 5) # define __attribute__(Spec) /* empty */ # endif /* The __-protected variants of `format' and `printf' attributes are accepted by gcc versions 2.6.4 (effectively 2.7) and later. */ # if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 7) # define __format__ format # define __printf__ printf # endif #endif 2006-03-25 Jim Meyering <jim(a)meyering.net> * src/virsh.c (vshPrint, vshError): Add gcc's __printf__ attribute. * src/xml.h (virBufferVSprintf): Likewise. Index: src/xml.h =================================================================== RCS file: /data/cvs/libvirt/src/xml.h,v retrieving revision 1.3 diff -u -p -r1.3 xml.h --- src/xml.h 15 Mar 2006 12:13:25 -0000 1.3 +++ src/xml.h 25 Mar 2006 10:56:27 -0000 @@ -25,7 +25,8 @@ extern "C" { }; int virBufferAdd(virBufferPtr buf, const char *str, int len); - int virBufferVSprintf(virBufferPtr buf, const char *format, ...); + int virBufferVSprintf(virBufferPtr buf, const char *format, ...) + __attribute__ ((__format__ (__printf__, 2, 3))); char *virDomainParseXMLDesc(const char *xmldesc, char **name); #ifdef __cplusplus Index: src/virsh.c =================================================================== RCS file: /data/cvs/libvirt/src/virsh.c,v retrieving revision 1.21 diff -u -p -r1.21 virsh.c --- src/virsh.c 15 Mar 2006 12:13:25 -0000 1.21 +++ src/virsh.c 25 Mar 2006 10:56:28 -0000 @@ -177,8 +177,8 @@ typedef struct __vshControl { static vshCmdDef commands[]; -static void vshError(vshControl * ctl, int doexit, const char *format, - ...); +static void vshError(vshControl * ctl, int doexit, const char *format, ...) + __attribute__ ((__format__ (__printf__, 3, 4))); static int vshInit(vshControl * ctl); static int vshDeinit(vshControl * ctl); static void vshUsage(vshControl * ctl, const char *cmdname); @@ -198,8 +198,9 @@ static virDomainPtr vshCommandOptDomain( const char *optname, char **name); -static void vshPrint(vshControl * ctl, vshOutType out, const char *format, - ...); +static void vshPrint(vshControl * ctl, vshOutType out, const char *format, ...) + __attribute__ ((__format__ (__printf__, 3, 4))); + ; static const char *vshDomainStateToString(int state);

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[Libvir] Patch for include file syntax
by Daniel P. Berrange 25 Mar '06

25 Mar '06

When doing an out-of-tree build of code which uses virterror.h, one gets a build failure, because when deployed virterror.h lives in subdir of the include directory rather than the top level In file included from Virt.xs:25: /usr/include/libvirt/virterror.h:17:21: error: libvirt.h: No such file or directory In file included from Virt.xs:25: /usr/include/libvirt/virterror.h:62: error: expected specifier-qualifier-list before âvirConnectPtrâ /usr/include/libvirt/virterror.h:122: error: expected â)â before âconnâ /usr/include/libvirt/virterror.h:123: error: expected â)â before âconnâ /usr/include/libvirt/virterror.h:129: error: expected â)â before âconnâ /usr/include/libvirt/virterror.h:132: error: expected â)â before âconnâ This is fixable by making virterror.h use "..." instead of <...> to include libvirt.h. Attaching a patch to fix this Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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[Libvir] Patch for pkg-config file cflags
by Daniel P. Berrange 24 Mar '06

24 Mar '06

The libvirt.pc.in file has an empty field for the cflags variable, so if you install libvirt into any prefix which is not in the compiler's default include file search path the header files won't be found when compiling applications. Attching a patch which corrects the pkg-config file for libvirt Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|

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