Re: [Libvir] [PATCH] Allow modifying existing block device, making virDomainAttachDevice modify the device if it already exists

The attached patch adds code to xend_internal.c:xenDomainAttachDevice that checks to see if the device mentioned in the passed-in XML already exists, and if so calls op_device_configure to modify the device. It is particularly useful for connecting and disconnecting a hardware cdrom device to an FV guest. I considered making new API a la virDomainModifyDevice, but decided overloading virDomainAttachDevice was cleaner (and didn't change existing API). I have tested the patch on f7 with xen 3.1 and a windows 2000 guest. Since the patch merely wraps Xen's device_configure call, we're not adding much risk of breakage.

diff -ruN libvirt.orig/src/xend_internal.c libvirt/src/xend_internal.c --- libvirt.orig/src/xend_internal.c 2007-09-06 11:28:05.000000000 -0400 +++ libvirt/src/xend_internal.c 2007-09-06 10:47:25.000000000 -0400 @@ -3087,6 +3087,7 @@ char *sexpr, *conf, *str; int hvm = 0, ret; xenUnifiedPrivatePtr priv; + char class[8], ref[80]; if ((domain == NULL) || (domain->conn == NULL) || (domain->name == NULL)) { virXendError((domain ? domain->conn : NULL), VIR_ERR_INVALID_ARG, @@ -3116,8 +3117,16 @@ *(conf + strlen(conf) -1) = 0; /* suppress final ) */ } else conf = sexpr; - ret = xend_op(domain->conn, domain->name, "op", "device_create", - "config", conf, NULL); + if (virDomainXMLDevID(domain, xml, class, ref)) { + /* device doesn't exist, define it */ + ret = xend_op(domain->conn, domain->name, "op", "device_create", + "config", conf, NULL); + } + else { + /* device exists, attempt to modify it */ + ret = xend_op(domain->conn, domain->name, "op", "device_configure", + "config", conf, "dev", ref, NULL); + } free(sexpr); return ret; }