libxl: In libxl_set_vcpuonline check for maximum number of VCPUs against the cpumap.

There is no sense in trying to online (or offline) CPUs when the size of
cpumap is greater than the maximum number of VCPUs the guest can go to.

As such fail the operation if the count of CPUs to online is greater
than what the guest started with. For the offline case we do not
check (as the bits are unset in the cpumap) and let it go through.

We coalesce some of the underlying libxl_set_vcpuonline code
together which was duplicated in QMP and XenStore codepaths.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

(cherry picked from commit d83bf9d224)
Conflicts:
	tools/libxl/libxl.c
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

(cherry picked from commit 0d8cbcad03)
Conflicts:
	tools/libxl/libxl.c
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

(cherry picked from commit ca0f468192)
Conflicts:
	tools/libxl/libxl.c
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxl/libxl.c

@@ -4254,23 +4254,19 @@ int libxl_domain_get_nodeaffinity(libxl_ctx *ctx, uint32_t domid,
 }
 
 static int libxl__set_vcpuonline_xenstore(libxl__gc *gc, uint32_t domid,
-                                         libxl_bitmap *cpumap)
+                                         libxl_bitmap *cpumap,
+                                         const libxl_dominfo *info)
 {
-    libxl_dominfo info;
     char *dompath;
     xs_transaction_t t;
     int i, rc = ERROR_FAIL;
 
-    if (libxl_domain_info(CTX, &info, domid) < 0) {
-        LOGE(ERROR, "getting domain info list");
-        goto out;
-    }
     if (!(dompath = libxl__xs_get_dompath(gc, domid)))
         goto out;
 
 retry_transaction:
     t = xs_transaction_start(CTX->xsh);
-    for (i = 0; i <= info.vcpu_max_id; i++)
+    for (i = 0; i <= info->vcpu_max_id; i++)
         libxl__xs_write(gc, t,
                        libxl__sprintf(gc, "%s/cpu/%u/availability", dompath, i),
                        "%s", libxl_bitmap_test(cpumap, i) ? "online" : "offline");
@@ -4284,16 +4280,12 @@ out:
 }
 
 static int libxl__set_vcpuonline_qmp(libxl__gc *gc, uint32_t domid,
-                                     libxl_bitmap *cpumap)
+                                     libxl_bitmap *cpumap,
+                                     const libxl_dominfo *info)
 {
-    libxl_dominfo info;
     int i;
 
-    if (libxl_domain_info(CTX, &info, domid) < 0) {
-        LOGE(ERROR, "getting domain info list");
-        return ERROR_FAIL;
-    }
-    for (i = 0; i <= info.vcpu_max_id; i++) {
+    for (i = 0; i <= info->vcpu_max_id; i++) {
         if (libxl_bitmap_test(cpumap, i)) {
             /* Return value is ignore because it does not tell anything useful
              * on the completion of the command.
@@ -4309,17 +4301,35 @@ static int libxl__set_vcpuonline_qmp(libxl__gc *gc, uint32_t domid,
 int libxl_set_vcpuonline(libxl_ctx *ctx, uint32_t domid, libxl_bitmap *cpumap)
 {
     GC_INIT(ctx);
-    int rc;
+    int rc, maxcpus;
+    libxl_dominfo info;
+
+    rc = libxl_domain_info(CTX, &info, domid);
+    if (rc < 0) {
+        LOGE(ERROR, "getting domain info list");
+        goto out;
+    }
+
+    maxcpus = libxl_bitmap_count_set(cpumap);
+    if (maxcpus > info.vcpu_max_id + 1)
+    {
+        LOGE(ERROR, "Requested %d VCPUs, however maxcpus is %d!",
+             maxcpus, info.vcpu_max_id + 1);
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
     switch (libxl__device_model_version_running(gc, domid)) {
     case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN_TRADITIONAL:
-        rc = libxl__set_vcpuonline_xenstore(gc, domid, cpumap);
+        rc = libxl__set_vcpuonline_xenstore(gc, domid, cpumap, &info);
         break;
     case LIBXL_DEVICE_MODEL_VERSION_QEMU_XEN:
-        rc = libxl__set_vcpuonline_qmp(gc, domid, cpumap);
+        rc = libxl__set_vcpuonline_qmp(gc, domid, cpumap, &info);
         break;
     default:
         rc = ERROR_INVAL;
     }
+out:
     GC_FREE;
     return rc;
 }