add documentation for multi-core features

extend QEMU's internal help and man page to cover the recently
added multi-core feature.
Signed-off-by: NAndre Przywara <andre.przywara@amd.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

qemu-options.hx

@@ -39,15 +39,23 @@ Select CPU model (-cpu ? for list and additional feature selection)
 ETEXI
 
 DEF("smp", HAS_ARG, QEMU_OPTION_smp,
-    "-smp n[,maxcpus=cpus]\n"
+    "-smp n[,maxcpus=cpus][,cores=cores][,threads=threads][,sockets=sockets]\n"
     "                set the number of CPUs to 'n' [default=1]\n"
     "                maxcpus= maximum number of total cpus, including\n"
-    "                offline CPUs for hotplug etc.\n")
+    "                  offline CPUs for hotplug etc.\n"
+    "                cores= number of CPU cores on one socket\n"
+    "                threads= number of threads on one CPU core\n"
+    "                sockets= number of discrete sockets in the system\n")
 STEXI
-@item -smp @var{n}
+@item -smp @var{n}[,cores=@var{cores}][,threads=@var{threads}][,sockets=@var{sockets}][,maxcpus=@var{maxcpus}]
 Simulate an SMP system with @var{n} CPUs. On the PC target, up to 255
 CPUs are supported. On Sparc32 target, Linux limits the number of usable CPUs
 to 4.
+For the PC target, the number of @var{cores} per socket, the number
+of @var{threads} per cores and the total number of @var{sockets} can be
+specified. Missing values will be computed. If any on the three values is
+given, the total number of CPUs @var{n} can be omitted. @var{maxcpus}
+specifies the maximum number of hotpluggable CPUs.
 ETEXI
 
 DEF("numa", HAS_ARG, QEMU_OPTION_numa,