tools: Pass max_vcpus to XEN_DOMCTL_createdomain

XEN_DOMCTL_max_vcpus is a mandatory hypercall, but nothing actually prevents a
toolstack from unpausing a domain with no vcpus.

Originally, d->vcpus[] was an embedded array in struct domain, but c/s
fb442e217 "x86_64: allow more vCPU-s per guest" in Xen 4.0 altered it to being
dynamically allocated.  A side effect of this is that d->vcpu[] is NULL until
XEN_DOMCTL_max_vcpus has completed, but a lot of hypercalls blindly
dereference it.

Even today, the behaviour of XEN_DOMCTL_max_vcpus is a mandatory singleton
call which can't change the number of vcpus once a value has been chosen.

In preparation to remote the hypercall, extend xen_domctl_createdomain with
the a max_vcpus field and arrange for all callers to pass the appropriate
value.  There is no change in construction behaviour yet, but later patches
will rearrange the hypervisor internals.

For the python stubs, extend the domain_create keyword list to take a
max_vcpus parameter, in lieu of deleting the pyxc_domain_max_vcpus function.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

tools/helpers/init-xenstore-domain.c

@@ -66,6 +66,7 @@ static int build(xc_interface *xch)
     struct xen_domctl_createdomain config = {
         .ssidref = SECINITSID_DOMU,
         .flags = XEN_DOMCTL_CDF_xs_domain,
+        .max_vcpus = 1,
         .max_evtchn_port = -1, /* No limit. */
 
         /*
@@ -100,7 +101,7 @@ static int build(xc_interface *xch)
         fprintf(stderr, "xc_domain_create failed\n");
         goto err;
     }
-    rv = xc_domain_max_vcpus(xch, domid, 1);
+    rv = xc_domain_max_vcpus(xch, domid, config.max_vcpus);
     if ( rv )
     {
         fprintf(stderr, "xc_domain_max_vcpus failed\n");

tools/libxl/libxl_create.c

@@ -566,6 +566,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
     if (!libxl_domid_valid_guest(*domid)) {
         struct xen_domctl_createdomain create = {
             .ssidref = info->ssidref,
+            .max_vcpus = b_info->max_vcpus,
             .max_evtchn_port = b_info->event_channels,
             .max_grant_frames = b_info->max_grant_frames,
             .max_maptrack_frames = b_info->max_maptrack_frames,

tools/ocaml/libs/xc/xenctrl.ml

@@ -63,6 +63,7 @@ type domctl_create_config =
 	ssidref: int32;
 	handle: string;
 	flags: domain_create_flag list;
+	max_vcpus: int;
 	max_evtchn_port: int;
 	max_grant_frames: int;
 	max_maptrack_frames: int;

tools/ocaml/libs/xc/xenctrl.mli

@@ -55,6 +55,7 @@ type domctl_create_config = {
   ssidref: int32;
   handle: string;
   flags: domain_create_flag list;
+  max_vcpus: int;
   max_evtchn_port: int;
   max_grant_frames: int;
   max_maptrack_frames: int;

tools/ocaml/libs/xc/xenctrl_stubs.c

@@ -128,15 +128,17 @@ CAMLprim value stub_xc_domain_create(value xch, value config)
 #define VAL_SSIDREF             Field(config, 0)
 #define VAL_HANDLE              Field(config, 1)
 #define VAL_FLAGS               Field(config, 2)
-#define VAL_MAX_EVTCHN_PORT     Field(config, 3)
-#define VAL_MAX_GRANT_FRAMES    Field(config, 4)
-#define VAL_MAX_MAPTRACK_FRAMES Field(config, 5)
-#define VAL_ARCH                Field(config, 6)
+#define VAL_MAX_VCPUS           Field(config, 3)
+#define VAL_MAX_EVTCHN_PORT     Field(config, 4)
+#define VAL_MAX_GRANT_FRAMES    Field(config, 5)
+#define VAL_MAX_MAPTRACK_FRAMES Field(config, 6)
+#define VAL_ARCH                Field(config, 7)
 
 	uint32_t domid = 0;
 	int result;
 	struct xen_domctl_createdomain cfg = {
 		.ssidref = Int32_val(VAL_SSIDREF),
+		.max_vcpus = Int_val(VAL_MAX_VCPUS),
 		.max_evtchn_port = Int_val(VAL_MAX_EVTCHN_PORT),
 		.max_grant_frames = Int_val(VAL_MAX_GRANT_FRAMES),
 		.max_maptrack_frames = Int_val(VAL_MAX_MAPTRACK_FRAMES),
@@ -178,6 +180,7 @@ CAMLprim value stub_xc_domain_create(value xch, value config)
 #undef VAL_MAX_MAPTRACK_FRAMES
 #undef VAL_MAX_GRANT_FRAMES
 #undef VAL_MAX_EVTCHN_PORT
+#undef VAL_MAX_VCPUS
 #undef VAL_FLAGS
 #undef VAL_HANDLE
 #undef VAL_SSIDREF

tools/python/xen/lowlevel/xc/xc.c

@@ -125,16 +125,19 @@ static PyObject *pyxc_domain_create(XcObject *self,
             0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef,
             0xde, 0xad, 0xbe, 0xef, 0xde, 0xad, 0xbe, 0xef,
         },
+        .max_vcpus = 1,
         .max_evtchn_port = -1, /* No limit. */
         .max_grant_frames = 32,
         .max_maptrack_frames = 1024,
     };
 
-    static char *kwd_list[] = { "domid", "ssidref", "handle", "flags", "target", NULL };
+    static char *kwd_list[] = { "domid", "ssidref", "handle", "flags",
+                                "target", "max_vcpus", NULL };
 
-    if ( !PyArg_ParseTupleAndKeywords(args, kwds, "|iiOii", kwd_list,
+    if ( !PyArg_ParseTupleAndKeywords(args, kwds, "|iiOiii", kwd_list,
                                       &dom, &config.ssidref, &pyhandle,
-                                      &config.flags, &target))
+                                      &config.flags, &target,
+                                      &config.max_vcpus) )
         return NULL;
     if ( pyhandle != NULL )
     {

xen/include/public/domctl.h

@@ -70,6 +70,7 @@ struct xen_domctl_createdomain {
      * Various domain limits, which impact the quantity of resources (global
      * mapping space, xenheap, etc) a guest may consume.
      */
+    uint32_t max_vcpus;
     uint32_t max_evtchn_port;
     uint32_t max_grant_frames;
     uint32_t max_maptrack_frames;