From: Michal Privoznik <mprivozn@redhat.com>
Date: Tue, 22 Feb 2022 08:02:17 +0000 (+0100)
Subject: qemu: Don't ignore failure when building default memory backend
X-Git-Tag: v8.1.0-rc1~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a6929d62cf5ca6bef076876f3354375f3a719df0;p=thirdparty%2Flibvirt.git

qemu: Don't ignore failure when building default memory backend

When building the default memory backend (which has id='pc.ram')
and no guest NUMA is configured then
qemuBuildMemCommandLineMemoryDefaultBackend() is called. However,
its return value is ignored which means that on invalid
configuration (e.g. when non-existent hugepage size was
requested) an error is reported into the logs but QEMU is started
anyway. And while QEMU does error out its error message doesn't
give much clue what's going on:

  qemu-system-x86_64: Memory backend 'pc.ram' not found

While at it, introduce a test case. While I could chose a nice
looking value (e.g. 4MiB) that's exactly what I wanted to avoid,
because while such value might not be possible on x84_64 it may
be possible on other arches (e.g. ppc is notoriously known for
supporting wide range of HP sizes). Let's stick with obviously
wrong value of 5MiB.

Reported-by: Charles Polisher <chas@chasmo.org>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 2c963a7297..c836799888 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -7369,8 +7369,9 @@ qemuBuildMemCommandLine(virCommand *cmd,
          * regular memory because -mem-path and -mem-prealloc are obsolete.
          * However, if domain has one or more NUMA nodes then there is no
          * default RAM and we mustn't generate the memory object. */
-        if (!virDomainNumaGetNodeCount(def->numa))
-            qemuBuildMemCommandLineMemoryDefaultBackend(cmd, def, priv, defaultRAMid);
+        if (!virDomainNumaGetNodeCount(def->numa) &&
+            qemuBuildMemCommandLineMemoryDefaultBackend(cmd, def, priv, defaultRAMid) < 0)
+            return -1;
     } else {
         /*
          * Add '-mem-path' (and '-mem-prealloc') parameter here if
diff --git a/tests/qemuxml2argvdata/hugepages-default-5M.x86_64-latest.err b/tests/qemuxml2argvdata/hugepages-default-5M.x86_64-latest.err
new file mode 100644
index 0000000000..bf5e54c9e4
--- /dev/null
+++ b/tests/qemuxml2argvdata/hugepages-default-5M.x86_64-latest.err
@@ -0,0 +1 @@
+internal error: Unable to find any usable hugetlbfs mount for 5120 KiB
diff --git a/tests/qemuxml2argvdata/hugepages-default-5M.xml b/tests/qemuxml2argvdata/hugepages-default-5M.xml
new file mode 100644
index 0000000000..280ea4bb71
--- /dev/null
+++ b/tests/qemuxml2argvdata/hugepages-default-5M.xml
@@ -0,0 +1,27 @@
+<domain type="kvm">
+  <name>NonExistentPageSize</name>
+  <uuid>21433e10-aea8-434a-8f81-55781c2e9035</uuid>
+  <memory unit="KiB">4194304</memory>
+  <currentMemory unit="KiB">4194304</currentMemory>
+  <memoryBacking>
+    <hugepages>
+      <page size="5" unit="MiB"/>
+    </hugepages>
+  </memoryBacking>
+  <vcpu placement="static">2</vcpu>
+  <os>
+    <type arch="x86_64" machine="pc">hvm</type>
+  </os>
+  <features>
+    <acpi/>
+    <apic/>
+    <pae/>
+  </features>
+  <clock offset="utc"/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>restart</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index 9378125da1..ce475df466 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -1272,6 +1272,7 @@ mymain(void)
     DO_TEST("hugepages-default", QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST("hugepages-default-2M", QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST("hugepages-default-system-size", QEMU_CAPS_OBJECT_MEMORY_FILE);
+    DO_TEST_CAPS_LATEST_FAILURE("hugepages-default-5M");
     DO_TEST_PARSE_ERROR_NOCAPS("hugepages-default-1G-nodeset-2M");
     DO_TEST("hugepages-nodeset", QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST_PARSE_ERROR("hugepages-nodeset-nonexist",