[libvirt] [RFC PATCH 03/17] qemu: use memory-backend-memfd if possible

[marcandre.lureau at redhat.com]

From: Marc-André Lureau <marcandre.lureau at redhat.com>

When the memory is shared and the source isn't specified to be a file,
we can make use of memory-backend-memfd. Sealing is enabled by default
in qemu, hugepage is easier to setup, which makes it a better choice
than memory-backend-file.

Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
---
 src/qemu/qemu_command.c           | 20 ++++++++++++++++---
 tests/qemuxml2argvdata/memfd.args | 28 +++++++++++++++++++++++++++
 tests/qemuxml2argvdata/memfd.xml  | 32 +++++++++++++++++++++++++++++++
 tests/qemuxml2argvtest.c          |  2 ++
 4 files changed, 79 insertions(+), 3 deletions(-)
 create mode 100644 tests/qemuxml2argvdata/memfd.args
 create mode 100644 tests/qemuxml2argvdata/memfd.xml

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index f1235099b2..45ab1f85ae 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -3137,7 +3137,21 @@ qemuBuildMemoryBackendProps(virJSONValuePtr *backendProps,
     if (!(props = virJSONValueNewObject()))
         return -1;
 
-    if (useHugepage || mem->nvdimmPath || memAccess ||
+    if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_MEMFD) &&
+        memAccess == VIR_DOMAIN_MEMORY_ACCESS_SHARED &&
+        !mem->nvdimmPath &&
+        def->mem.source != VIR_DOMAIN_MEMORY_SOURCE_FILE) {
+
+        backendType = "memory-backend-memfd";
+
+        if (useHugepage &&
+            virJSONValueObjectAdd(props,
+                                  "b:hugetlb", true,
+                                  "U:hugetlbsize", pagesize * 1024,
+                                  NULL) < 0)
+            goto cleanup;
+
+    } else if (useHugepage || mem->nvdimmPath || memAccess ||
         def->mem.source == VIR_DOMAIN_MEMORY_SOURCE_FILE) {
 
         if (useHugepage) {
@@ -7670,8 +7684,8 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,
      * need to check which approach to use */
     for (i = 0; i < ncells; i++) {
         if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_RAM) ||
-            virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE)) {
-
+            virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_FILE) ||
+            virQEMUCapsGet(qemuCaps, QEMU_CAPS_OBJECT_MEMORY_MEMFD)) {
 
             if (implicit)
                 rc = qemuBuildMemoryBackendStr(def, cfg, "ram-node", -1,
diff --git a/tests/qemuxml2argvdata/memfd.args b/tests/qemuxml2argvdata/memfd.args
new file mode 100644
index 0000000000..dda8e272ea
--- /dev/null
+++ b/tests/qemuxml2argvdata/memfd.args
@@ -0,0 +1,28 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-i686 \
+-name QEMUGuest1 \
+-S \
+-machine pc,accel=tcg,usb=off,dump-guest-core=off \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-object memory-backend-memfd,id=ram-node,size=224395264 \
+-numa node,nodeid=0,memdev=ram-node \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-boot c \
+-usb \
+-drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
+-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/memfd.xml b/tests/qemuxml2argvdata/memfd.xml
new file mode 100644
index 0000000000..c60b169169
--- /dev/null
+++ b/tests/qemuxml2argvdata/memfd.xml
@@ -0,0 +1,32 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219136</memory>
+  <currentMemory unit='KiB'>219136</currentMemory>
+  <memoryBacking>
+    <access mode='shared'/>
+  </memoryBacking>
+  <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-system-i686</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='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index a929e4314e..47bd2ab867 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -945,6 +945,8 @@ mymain(void)
     DO_TEST("pmu-feature", NONE);
     DO_TEST("pmu-feature-off", NONE);
 
+    DO_TEST("memfd",
+            QEMU_CAPS_OBJECT_MEMORY_MEMFD);
     DO_TEST("hugepages", NONE);
     DO_TEST("hugepages-numa",
             QEMU_CAPS_PIIX_DISABLE_S3, QEMU_CAPS_PIIX_DISABLE_S4,
-- 
2.18.0.129.ge3331758f1