vcpu: improve vcpu support in qemu command line

* src/qemu/qemu_conf.c (qemuParseCommandLineSmp): Distinguish
between vcpus and maxvcpus, for new enough qemu.
* tests/qemuargv2xmltest.c (mymain): Add new test.
* tests/qemuxml2argvtest.c (mymain): Likewise.
* tests/qemuxml2xmltest.c (mymain): Likewise.
* tests/qemuxml2argvdata/qemuxml2argv-smp.args: New file.

src/qemu/qemu_conf.c

@@ -3714,6 +3714,8 @@ qemuBuildSmpArgStr(const virDomainDefPtr def,
     virBufferVSprintf(&buf, "%u", def->vcpus);
 
     if ((qemuCmdFlags & QEMUD_CMD_FLAG_SMP_TOPOLOGY)) {
+        if (def->vcpus != def->maxvcpus)
+            virBufferVSprintf(&buf, ",maxcpus=%u", def->maxvcpus);
         /* sockets, cores, and threads are either all zero
          * or all non-zero, thus checking one of them is enough */
         if (def->cpu && def->cpu->sockets) {
@@ -3726,12 +3728,12 @@ qemuBuildSmpArgStr(const virDomainDefPtr def,
             virBufferVSprintf(&buf, ",cores=%u", 1);
             virBufferVSprintf(&buf, ",threads=%u", 1);
         }
-    }
-    if (def->vcpus != def->maxvcpus) {
+    } else if (def->vcpus != def->maxvcpus) {
         virBufferFreeAndReset(&buf);
+        /* FIXME - consider hot-unplugging cpus after boot for older qemu */
         qemuReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                         _("setting current vcpu count less than maximum is "
-                          "not supported yet"));
+                          "not supported with this QEMU binary"));
         return NULL;
     }
 
@@ -6153,6 +6155,7 @@ qemuParseCommandLineSmp(virDomainDefPtr dom,
     unsigned int sockets = 0;
     unsigned int cores = 0;
     unsigned int threads = 0;
+    unsigned int maxcpus = 0;
     int i;
     int nkws;
     char **kws;
@@ -6180,12 +6183,14 @@ qemuParseCommandLineSmp(virDomainDefPtr dom,
                 cores = n;
             else if (STREQ(kws[i], "threads"))
                 threads = n;
+            else if (STREQ(kws[i], "maxcpus"))
+                maxcpus = n;
             else
                 goto syntax;
         }
     }
 
-    dom->maxvcpus = dom->vcpus;
+    dom->maxvcpus = maxcpus ? maxcpus : dom->vcpus;
 
     if (sockets && cores && threads) {
         virCPUDefPtr cpu;

tests/qemuargv2xmltest.c

@@ -221,6 +221,8 @@ mymain(int argc, char **argv)
 
     DO_TEST("hostdev-pci-address");
 
+    DO_TEST("smp");
+
     DO_TEST_FULL("restore-v1", 0, "stdio");
     DO_TEST_FULL("restore-v2", 0, "stdio");
     DO_TEST_FULL("restore-v2", 0, "exec:cat");

tests/qemuxml2argvdata/qemuxml2argv-smp.args

+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu -S -M pc -m 214 -smp 1,maxcpus=2,sockets=2,cores=1,threads=1 -nographic -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -hda /dev/HostVG/QEMUGuest1 -net none -serial none -parallel none -usb

tests/qemuxml2argvtest.c

@@ -385,6 +385,8 @@ mymain(int argc, char **argv)
 
     DO_TEST("qemu-ns", 0);
 
+    DO_TEST("smp", QEMUD_CMD_FLAG_SMP_TOPOLOGY);
+
     free(driver.stateDir);
     virCapabilitiesFree(driver.caps);
 

tests/qemuxml2xmltest.c

@@ -180,6 +180,8 @@ mymain(int argc, char **argv)
     DO_TEST("encrypted-disk");
     DO_TEST("memtune");
 
+    DO_TEST("smp");
+
     /* These tests generate different XML */
     DO_TEST_DIFFERENT("balloon-device-auto");
     DO_TEST_DIFFERENT("channel-virtio-auto");