xenstore: add XS_RESUME command; export it to xend.

This clears the shutdown flag for a domain in xenstore, allowing
subsequent shutdowns of the same domain to fire the appropriate
watches.

Signed-off-by: Brendan Cully <brendan@cs.ubc.ca>

tools/python/xen/lowlevel/xs/xs.c

@@ -618,6 +618,33 @@ static PyObject *xspy_introduce_domain(XsHandle *self, PyObject *args)
     return none(result);
 }
 
+#define xspy_resume_domain_doc "\n"                                \
+	"Tell xenstore to clear its shutdown flag for a domain.\n" \
+	"This ensures that a subsequent shutdown will fire the\n"  \
+	"appropriate watches.\n"                                   \
+	" dom [int]: domain id\n"			           \
+        "\n"						           \
+        "Returns None on success.\n"				   \
+        "Raises xen.lowlevel.xs.Error on error.\n"
+
+static PyObject *xspy_resume_domain(XsHandle *self, PyObject *args)
+{
+    uint32_t dom;
+
+    struct xs_handle *xh = xshandle(self);
+    bool result = 0;
+
+    if (!xh)
+        return NULL;
+    if (!PyArg_ParseTuple(args, "i", &dom))
+        return NULL;
+
+    Py_BEGIN_ALLOW_THREADS
+    result = xs_resume_domain(xh, dom);
+    Py_END_ALLOW_THREADS
+
+    return none(result);
+}
 
 #define xspy_release_domain_doc "\n"					\
 	"Tell xenstore to release its channel to a domain.\n"		\
@@ -789,6 +816,7 @@ static PyMethodDef xshandle_methods[] = {
     XSPY_METH(transaction_start, METH_NOARGS),
     XSPY_METH(transaction_end,   METH_VARARGS | METH_KEYWORDS),
     XSPY_METH(introduce_domain,  METH_VARARGS),
+    XSPY_METH(resume_domain,     METH_VARARGS),
     XSPY_METH(release_domain,    METH_VARARGS),
     XSPY_METH(close,             METH_NOARGS),
     XSPY_METH(get_domain_path,   METH_VARARGS),

tools/python/xen/xend/XendDomainInfo.py

@@ -45,7 +45,7 @@ from xen.xend.XendBootloader import bootloader
 from xen.xend.XendError import XendError, VmError
 from xen.xend.XendDevices import XendDevices
 from xen.xend.xenstore.xstransact import xstransact, complete
-from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain
+from xen.xend.xenstore.xsutil import GetDomainPath, IntroduceDomain, ResumeDomain
 from xen.xend.xenstore.xswatch import xswatch
 from xen.xend.XendConstants import *
 from xen.xend.XendAPIConstants import *
@@ -1545,6 +1545,7 @@ class XendDomainInfo:
         try:
             if self.domid is not None:
                 xc.domain_resume(self.domid)
+                ResumeDomain(self.domid)
         except:
             log.exception("XendDomainInfo.resume: xc.domain_resume failed on domain %s." % (str(self.domid)))
 

tools/python/xen/xend/xenstore/xsutil.py

@@ -24,3 +24,6 @@ def IntroduceDomain(domid, page, port):
 
 def GetDomainPath(domid):
     return xshandle().get_domain_path(domid)
+
+def ResumeDomain(domid):
+    return xshandle().resume_domain(domid)