[Libvir] Re: [PATCH] Re: Proposal: Check availability of driver calls (repost)

Daniel Veillard wrote: >On Tue, Jul 31, 2007 at 02:09:20PM +0100, Richard W.M. Jones wrote: >>Daniel Veillard wrote: >>>I'm not 100% sure we want to >>>expose this as a library API though, at least not in that way. >>I should just say in case I wasn't 100% clear that this is just a driver >>API. Nothing should be exposed from libvirt. > > Then feature detection + versionning in the protocol. I'm Here's a patch. [I'm going to start a separate thread on the issue of exporting calls to libvirtd.] Rich. -- Emerging Technologies, Red Hat - http://et.redhat.com/~rjones/ Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SL4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 03798903

Index: src/driver.h =================================================================== RCS file: /data/cvs/libvirt/src/driver.h,v retrieving revision 1.32 diff -u -p -r1.32 driver.h --- src/driver.h 27 Jul 2007 23:23:00 -0000 1.32 +++ src/driver.h 31 Jul 2007 14:20:02 -0000 @@ -44,12 +44,44 @@ typedef enum { VIR_DRV_OPEN_ERROR = -2, } virDrvOpenStatus; +/* Feature detection. This is a libvirt-private interface for determining + * what features are supported by the driver. + * + * The remote driver passes features through to the real driver at the + * remote end unmodified, except if you query a VIR_DRV_FEATURE_REMOTE* + * feature. + */ +typedef enum { + /* Driver supports V1-style virDomainMigrate, ie. domainMigratePrepare/ + * domainMigratePerform/domainMigrateFinish. + */ + VIR_DRV_FEATURE_MIGRATION_V1 = 1, + + /* Driver is not local. */ + VIR_DRV_FEATURE_REMOTE = 2, +} virDrvFeature;

+/* Internal feature-detection macro. Don't call drv->supports_feature + * directly, because it may be NULL, use this macro instead. + * + * Note that you must check for errors. + * + * Returns: + * >= 1 Feature is supported. + * 0 Feature is not supported. + * -1 Error. + */ +#define VIR_DRV_SUPPORTS_FEATURE(drv,conn,feature) \ + ((drv)->supports_feature ? (drv)->supports_feature((conn),(feature)) : 0) + typedef virDrvOpenStatus (*virDrvOpen) (virConnectPtr conn, const char *name, int flags); typedef int (*virDrvClose) (virConnectPtr conn); +typedef int + (*virDrvSupportsFeature) (virConnectPtr conn, virDrvFeature feature);

typedef const char * (*virDrvGetType) (virConnectPtr conn); typedef int @@ -202,6 +234,7 @@ struct _virDriver { unsigned long ver; /* the version of the backend */ virDrvOpen open; virDrvClose close; + virDrvSupportsFeature supports_feature;

virDrvGetType type; virDrvGetVersion version; virDrvGetHostname getHostname; Index: src/internal.h =================================================================== RCS file: /data/cvs/libvirt/src/internal.h,v retrieving revision 1.47 diff -u -p -r1.47 internal.h --- src/internal.h 25 Jul 2007 23:16:30 -0000 1.47 +++ src/internal.h 31 Jul 2007 14:20:03 -0000 @@ -229,6 +229,8 @@ int __virStateActive(void); #define virStateReload() __virStateReload() #define virStateActive() __virStateActive() +int __virDrvSupportsFeature (virConnectPtr conn, int feature); +

#ifdef __cplusplus } #endif /* __cplusplus */ Index: src/libvirt.c =================================================================== RCS file: /data/cvs/libvirt/src/libvirt.c,v retrieving revision 1.92 diff -u -p -r1.92 libvirt.c --- src/libvirt.c 27 Jul 2007 23:23:00 -0000 1.92 +++ src/libvirt.c 31 Jul 2007 14:20:04 -0000 @@ -540,6 +540,20 @@ virConnectClose(virConnectPtr conn) return (0); } +/* Not for public use. This function is part of the internal + * implementation of driver features in the remote case. + */ +int +__virDrvSupportsFeature (virConnectPtr conn, int feature) +{ + DEBUG("conn=%p, feature=%d", conn, feature); + + if (!VIR_IS_CONNECT(conn)) + return (-1); + + return VIR_DRV_SUPPORTS_FEATURE (conn->driver, conn, feature); +} +

/** * virConnectGetType: * @conn: pointer to the hypervisor connection Index: src/libvirt_sym.version =================================================================== RCS file: /data/cvs/libvirt/src/libvirt_sym.version,v retrieving revision 1.25 diff -u -p -r1.25 libvirt_sym.version --- src/libvirt_sym.version 26 Jun 2007 22:56:14 -0000 1.25 +++ src/libvirt_sym.version 31 Jul 2007 14:20:05 -0000 @@ -116,5 +116,7 @@ __virStateReload; __virStateActive; + __virDrvSupportsFeature; + local: *; }; Index: src/qemu_driver.c =================================================================== RCS file: /data/cvs/libvirt/src/qemu_driver.c,v retrieving revision 1.14 diff -u -p -r1.14 qemu_driver.c --- src/qemu_driver.c 30 Jul 2007 09:59:06 -0000 1.14 +++ src/qemu_driver.c 31 Jul 2007 14:20:07 -0000 @@ -2343,6 +2343,7 @@ static virDriver qemuDriver = { LIBVIR_VERSION_NUMBER, qemudOpen, /* open */ qemudClose, /* close */ + NULL, /* supports_feature */ qemudGetType, /* type */ qemudGetVersion, /* version */ NULL, /* hostname */ Index: src/remote_internal.c =================================================================== RCS file: /data/cvs/libvirt/src/remote_internal.c,v retrieving revision 1.16 diff -u -p -r1.16 remote_internal.c --- src/remote_internal.c 27 Jul 2007 23:23:00 -0000 1.16 +++ src/remote_internal.c 31 Jul 2007 14:20:10 -0000 @@ -1190,6 +1190,30 @@ remoteClose (virConnectPtr conn) return ret; } +static int +remoteSupportsFeature (virConnectPtr conn, virDrvFeature feature) +{ + remote_supports_feature_args args; + remote_supports_feature_ret ret; + GET_PRIVATE (conn, -1); + + /* VIR_DRV_FEATURE_REMOTE* features are handled directly. */ + switch (feature) { + case VIR_DRV_FEATURE_REMOTE: return 1; + default: /*FALLTHROUGH*/; + } + + args.feature = feature; + + memset (&ret, 0, sizeof ret); + if (call (conn, priv, 0, REMOTE_PROC_SUPPORTS_FEATURE, + (xdrproc_t) xdr_remote_supports_feature_args, (char *) &args, + (xdrproc_t) xdr_remote_supports_feature_ret, (char *) &ret) == -1) + return -1; + + return ret.supported; +} + /* Unfortunately this function is defined to return a static string. * Since the remote end always answers with the same type (for a * single connection anyway) we cache the type in the connection's @@ -2893,6 +2917,7 @@ static virDriver driver = { .ver = REMOTE_PROTOCOL_VERSION, .open = remoteOpen, .close = remoteClose, + .supports_feature = remoteSupportsFeature, .type = remoteType, .version = remoteVersion, .getHostname = remoteGetHostname, Index: src/test.c =================================================================== RCS file: /data/cvs/libvirt/src/test.c,v retrieving revision 1.43 diff -u -p -r1.43 test.c --- src/test.c 27 Jul 2007 23:23:00 -0000 1.43 +++ src/test.c 31 Jul 2007 14:20:12 -0000 @@ -1932,6 +1932,7 @@ static virDriver testDriver = { LIBVIR_VERSION_NUMBER, testOpen, /* open */ testClose, /* close */ + NULL, /* supports_feature */ NULL, /* type */ testGetVersion, /* version */ testGetHostname, /* hostname */ Index: qemud/remote.c =================================================================== RCS file: /data/cvs/libvirt/qemud/remote.c,v retrieving revision 1.6 diff -u -p -r1.6 remote.c --- qemud/remote.c 24 Jul 2007 14:21:03 -0000 1.6 +++ qemud/remote.c 31 Jul 2007 14:20:13 -0000 @@ -418,6 +418,18 @@ remoteDispatchClose (struct qemud_client } static int +remoteDispatchSupportsFeature (struct qemud_client *client, remote_message_header *req, + remote_supports_feature_args *args, remote_supports_feature_ret *ret) +{ + CHECK_CONN(client); + + ret->supported = __virDrvSupportsFeature (client->conn, args->feature); + if (ret->supported == -1) return -1; + + return 0; +} + +static int remoteDispatchGetType (struct qemud_client *client, remote_message_header *req, void *args ATTRIBUTE_UNUSED, remote_get_type_ret *ret) { Index: qemud/remote_protocol.x =================================================================== RCS file: /data/cvs/libvirt/qemud/remote_protocol.x,v retrieving revision 1.3 diff -u -p -r1.3 remote_protocol.x --- qemud/remote_protocol.x 26 Jun 2007 11:42:46 -0000 1.3 +++ qemud/remote_protocol.x 31 Jul 2007 14:20:13 -0000 @@ -170,6 +170,14 @@ struct remote_open_args { int flags; }; +struct remote_supports_feature_args { + int feature; +}; + +struct remote_supports_feature_ret { + int supported; +}; + struct remote_get_type_ret { remote_nonnull_string type; }; @@ -610,7 +618,8 @@ enum remote_procedure { REMOTE_PROC_DOMAIN_GET_SCHEDULER_TYPE = 56, REMOTE_PROC_DOMAIN_GET_SCHEDULER_PARAMETERS = 57, REMOTE_PROC_DOMAIN_SET_SCHEDULER_PARAMETERS = 58, - REMOTE_PROC_GET_HOSTNAME = 59 + REMOTE_PROC_GET_HOSTNAME = 59, + REMOTE_PROC_SUPPORTS_FEATURE = 60 }; /* Custom RPC structure. */