qemu: Implement setup of memory hotplug parameters

To enable memory hotplug the maximum memory size and slot count need to
be specified. As qemu supports now other units than mebibytes when
specifying memory, use the new interface in this case.

docs/formatdomain.html.in

@@ -725,7 +725,7 @@
         Note that due to alignment of the memory chunks added via memory
         hotplug the full size allocation specified by this element may be
         impossible to achieve.
-        <span class='since'>Since 1.2.14</span>
+        <span class='since'>Since 1.2.14 supported by the QEMU driver.</span>
       </dd>
 
       <dt><code>currentMemory</code></dt>

src/qemu/qemu_command.c

@@ -8492,13 +8492,35 @@ qemuBuildCommandLine(virConnectPtr conn,
     if (qemuDomainAlignMemorySizes(def) < 0)
         goto error;
 
-    /* Set '-m MB' based on maxmem, because the lower 'memory' limit
-     * is set post-startup using the balloon driver. If balloon driver
-     * is not supported, then they're out of luck anyway.  Update the
-     * XML to reflect our rounding.
-     */
     virCommandAddArg(cmd, "-m");
+
+    if (def->mem.max_memory) {
+        if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_PC_DIMM)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("memory hotplug isn't supported by this QEMU binary"));
+            goto error;
+        }
+
+        /* due to guest support, qemu would silently enable NUMA with one node
+         * once the memory hotplug backend is enabled. To avoid possible
+         * confusion we will enforce user originated numa configuration along
+         * with memory hotplug. */
+        if (virDomainNumaGetNodeCount(def->numa) == 0) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("At least one numa node has to be configured when "
+                             "enabling memory hotplug"));
+            goto error;
+        }
+
+        /* Use the 'k' suffix to let qemu handle the units */
+        virCommandAddArgFormat(cmd, "size=%lluk,slots=%u,maxmem=%lluk",
+                               virDomainDefGetMemoryInitial(def),
+                               def->mem.memory_slots,
+                               def->mem.max_memory);
+
+    } else {
        virCommandAddArgFormat(cmd, "%llu", virDomainDefGetMemoryInitial(def) / 1024);
+    }
 
     if (def->mem.nhugepages && !virDomainNumaGetNodeCount(def->numa)) {
         const long system_page_size = virGetSystemPageSizeKB();

src/qemu/qemu_domain.c

@@ -1052,10 +1052,6 @@ qemuDomainDefPostParse(virDomainDefPtr def,
                                   VIR_DOMAIN_INPUT_BUS_USB) < 0)
         return -1;
 
-    /* memory hotplug tunables are not supported by this driver */
-    if (virDomainDefCheckUnsupportedMemoryHotplug(def) < 0)
-        return -1;
-
     return 0;
 }
 
@@ -2906,5 +2902,9 @@ qemuDomainAlignMemorySizes(virDomainDefPtr def)
     mem = virDomainDefGetMemoryInitial(def);
     virDomainDefSetMemoryInitial(def, VIR_ROUND_UP(mem, 1024));
 
+    /* Align maximum memory size. QEMU requires rounding to next 4KiB block.
+     * We'll take the "traditional" path and round it to 1MiB*/
+    def->mem.max_memory = VIR_ROUND_UP(def->mem.max_memory, 1024);
+
     return 0;
 }

tests/qemuxml2argvdata/qemuxml2argv-memory-hotplug-nonuma.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <maxMemory slots='9' unit='KiB'>1233456789</maxMemory>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <controller type='usb' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvdata/qemuxml2argv-memory-hotplug.args

+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu -S -M pc \
+-m size=219136k,slots=16,maxmem=1099511627776k \
+-smp 2 -numa node,nodeid=0,cpus=0-1,mem=214 \
+-nographic -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
+-usb -hda /dev/HostVG/QEMUGuest1 -net none -serial none -parallel none

tests/qemuxml2argvdata/qemuxml2argv-memory-hotplug.xml

+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <maxMemory slots='16' unit='KiB'>1099511627776</maxMemory>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <vcpu placement='static' cpuset='0-1'>2</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu>
+    <topology sockets='2' cores='1' threads='1'/>
+    <numa>
+      <cell id='0' cpus='0-1' memory='219136' unit='KiB'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='ide' index='0'/>
+    <controller type='usb' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1543,6 +1543,10 @@ mymain(void)
     DO_TEST_PARSE_ERROR("shmem-msi-only", NONE);
     DO_TEST("cpu-host-passthrough-features", QEMU_CAPS_KVM, QEMU_CAPS_CPU_HOST);
 
+    DO_TEST_FAILURE("memory-hotplug-nonuma", QEMU_CAPS_DEVICE_PC_DIMM);
+    DO_TEST_FAILURE("memory-hotplug", NONE);
+    DO_TEST("memory-hotplug", QEMU_CAPS_DEVICE_PC_DIMM, QEMU_CAPS_NUMA);
+
     virObjectUnref(driver.config);
     virObjectUnref(driver.caps);
     virObjectUnref(driver.xmlopt);

tests/qemuxml2xmltest.c

@@ -428,6 +428,9 @@ mymain(void)
     DO_TEST("smbios");
     DO_TEST("aarch64-aavmf-virtio-mmio");
 
+    DO_TEST("memory-hotplug");
+    DO_TEST("memory-hotplug-nonuma");
+
     virObjectUnref(driver.caps);
     virObjectUnref(driver.xmlopt);