qemu: Build command line for virtio-mem

Nothing special is happening here. All important changes were
done when for 'virtio-pmem' (adjusting the code to put virtio
memory on PCI bus, generating alias using
qemuDomainDeviceAliasIndex(). The only bit that might look
suspicious is no prealloc for virtio-mem. But if you think about
it, the whole purpose of this device is to change amount of
memory exposed to guest on the fly. There is no point in locking
the whole backend in memory.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

src/qemu/qemu_alias.c

@@ -475,8 +475,11 @@ qemuDeviceMemoryGetAliasID(virDomainDef *def,
     size_t i;
     int maxidx = 0;
 
-    /* virtio-pmem goes onto PCI bus and thus DIMM address is not valid */
-    if (!oldAlias && mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_PMEM)
+    /* virtio-pmem and virtio-mem go onto PCI bus and thus DIMM address is not
+     * valid */
+    if (!oldAlias &&
+        mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_PMEM &&
+        mem->model != VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM)
         return mem->info.addr.dimm.slot;
 
     for (i = 0; i < def->nmems; i++) {
@@ -523,6 +526,8 @@ qemuAssignDeviceMemoryAlias(virDomainDef *def,
         prefix = "virtiopmem";
         break;
     case VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM:
+        prefix = "virtiomem";
+        break;
     case VIR_DOMAIN_MEMORY_MODEL_NONE:
     case VIR_DOMAIN_MEMORY_MODEL_LAST:
     default:

src/qemu/qemu_command.c

@@ -3028,9 +3028,23 @@ qemuBuildMemoryBackendProps(virJSONValue **backendProps,
         virJSONValueObjectAdd(props, "b:x-use-canonical-path-for-ramblock-id", false, NULL) < 0)
         return -1;
 
-    if (!priv->memPrealloc &&
-        virJSONValueObjectAdd(props, "B:prealloc", prealloc, NULL) < 0)
-        return -1;
+    if (mem->model == VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM) {
+        /* Explicitly disable prealloc for virtio-mem as it's not supported
+         * currently. Warn users if their config would result in prealloc. */
+        if (priv->memPrealloc || prealloc) {
+            VIR_WARN("Memory preallocation is unsupported for virtio-mem memory devices");
+        }
+        if (priv->memPrealloc &&
+            virJSONValueObjectAppendBoolean(props, "prealloc", 0) < 0)
+            return -1;
+        if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_MEMORY_BACKEND_RESERVE) &&
+            virJSONValueObjectAppendBoolean(props, "reserve", 0) < 0)
+            return -1;
+    } else {
+        if (!priv->memPrealloc &&
+            virJSONValueObjectAdd(props, "B:prealloc", prealloc, NULL) < 0)
+            return -1;
+    }
 
     if (virJSONValueObjectAdd(props, "U:size", mem->size * 1024, NULL) < 0)
         return -1;
@@ -3210,6 +3224,9 @@ qemuBuildMemoryDeviceStr(const virDomainDef *def,
         break;
 
     case VIR_DOMAIN_MEMORY_MODEL_VIRTIO_MEM:
+        device = "virtio-mem-pci";
+        break;
+
     case VIR_DOMAIN_MEMORY_MODEL_NONE:
     case VIR_DOMAIN_MEMORY_MODEL_LAST:
     default:
@@ -3226,6 +3243,11 @@ qemuBuildMemoryDeviceStr(const virDomainDef *def,
     if (mem->labelsize)
         virBufferAsprintf(&buf, "label-size=%llu,", mem->labelsize * 1024);
 
+    if (mem->blocksize) {
+        virBufferAsprintf(&buf, "block-size=%llu,", mem->blocksize * 1024);
+        virBufferAsprintf(&buf, "requested-size=%llu,", mem->requestedsize * 1024);
+    }
+
     if (mem->uuid) {
         char uuidstr[VIR_UUID_STRING_BUFLEN];
 

tests/qemuxml2argvdata/memory-hotplug-virtio-mem.x86_64-latest.args

@@ -0,0 +1,41 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-QEMUGuest1 \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
+/usr/bin/qemu-system-i386 \
+-name guest=QEMUGuest1,debug-threads=on \
+-S \
+-object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/tmp/lib/domain--1-QEMUGuest1/master-key.aes"}' \
+-machine pc,accel=kvm,usb=off,dump-guest-core=off \
+-cpu qemu64 \
+-m size=2095104k,slots=16,maxmem=1099511627776k \
+-overcommit mem-lock=off \
+-smp 2,sockets=2,dies=1,cores=1,threads=1 \
+-object '{"qom-type":"memory-backend-ram","id":"ram-node0","size":2145386496}' \
+-numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \
+-object '{"qom-type":"memory-backend-ram","id":"memvirtiomem0","reserve":false,"size":1073741824}' \
+-device virtio-mem-pci,node=0,block-size=2097152,requested-size=536870912,memdev=memvirtiomem0,id=virtiomem0,bus=pci.0,addr=0x2 \
+-object '{"qom-type":"memory-backend-file","id":"memvirtiomem1","mem-path":"/dev/hugepages2M/libvirt/qemu/-1-QEMUGuest1","reserve":false,"size":2147483648,"host-nodes":[1,2,3],"policy":"bind"}' \
+-device virtio-mem-pci,node=0,block-size=2097152,requested-size=1073741824,memdev=memvirtiomem1,id=virtiomem1,bus=pci.0,addr=0x3 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,fd=1729,server=on,wait=off \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-boot strict=on \
+-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
+-blockdev '{"driver":"host_device","filename":"/dev/HostVG/QEMUGuest1","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
+-blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"raw","file":"libvirt-1-storage"}' \
+-device ide-hd,bus=ide.0,unit=0,drive=libvirt-1-format,id=ide0-0-0,bootindex=1 \
+-audiodev id=audio1,driver=none \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x4 \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
+-msg timestamp=on

tests/qemuxml2argvtest.c

@@ -3085,6 +3085,7 @@ mymain(void)
                  ARG_END);
     DO_TEST_CAPS_VER("memory-hotplug-virtio-pmem", "5.2.0");
     DO_TEST_CAPS_LATEST("memory-hotplug-virtio-pmem");
+    DO_TEST_CAPS_LATEST("memory-hotplug-virtio-mem");
 
     DO_TEST("machine-aeskeywrap-on-caps",
             QEMU_CAPS_AES_KEY_WRAP,