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[libvirt] [PATCH v3] xml: introduce startupPolicy for chardev device



[Problem]
Currently, guest OS's messages can be logged to a local disk of host OS
by creating chadevs with options below.
  -chardev file,id=charserial0,path=<log file's path> -device isa-serial,chardev=chardevserial0,id=serial0

When a hardware failure happens in the disk, qemu-kvm can't create the
chardevs. In this case, guest OS doesn't boot up.

Actually, there are users who don't desire that guest OS goes down due
to a hardware failure of a log disk only. Therefore, qemu should offer
some way to boot guest OS up even if the log disk is broken.

[Solution]
This patch supports startupPolicy for chardev.

The starupPolicy is introduced just in cases where chardev is "file"
because this patch aims for making guest OS boot up when a hardware
failure happens.

In other cases (pty, dev, pipe and unix) it is not introduced
because they don't access to hardware.

The policy works as follows.
  - If the value is "optional", guestOS boots up by dropping the chardev.
  - If other values are specified, guestOS fails to boot up. (the default)

Description about original startupPolicy attribute:
http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=e5a84d74a278

Signed-off-by: Seiji Aguchi <seiji aguchi hds com>
Signed-off-by: Eric Blake <eblake redhat com>
---
Change from v2
 - To pass "make check", add followings.
   - Add serial source optional testing.
   - check if startupPolicy is NULL in virDomainChrSourceDefParseXML().
   - Add xml format of startupPolicy in virDomainChrSourceDefFormat().

Patch v2 and comment from Eric Blake
 - https://www.redhat.com/archives/libvir-list/2013-May/msg01814.html
 - https://www.redhat.com/archives/libvir-list/2013-May/msg01943.html
---
 docs/formatdomain.html.in                          |   16 ++++++++-
 docs/schemas/domaincommon.rng                      |    3 ++
 src/conf/domain_conf.c                             |   22 +++++++++++-
 src/conf/domain_conf.h                             |    1 +
 src/qemu/qemu_process.c                            |   25 +++++++++++++-
 .../qemuxml2argv-serial-source-optional.args       |    9 +++++
 .../qemuxml2argv-serial-source-optional.xml        |   35 ++++++++++++++++++++
 tests/qemuxml2argvtest.c                           |    2 +
 tests/qemuxml2xmltest.c                            |    1 +
 tests/virt-aa-helper-test                          |    3 ++
 10 files changed, 113 insertions(+), 4 deletions(-)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.args
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.xml

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 7601aaa..5c9d4fb 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -4281,13 +4281,27 @@ qemu-kvm -net nic,model=? /dev/null
     <p>
       A file is opened and all data sent to the character
       device is written to the file.
+      <span class="since">Since 1.0.6</span>, it is possible to define
+      policy on what happens if the file is not accessible when
+      booting or migrating. This is done by
+      a <code>startupPolicy</code> attribute:
     </p>
 
+    <ul>
+     <li>If the value is "mandatory" (the default), the guest fails
+     to boot or migrate if the file is not found.</li>
+     <li>If the value is "optional", a missing file is at boot or
+     migration is substituted with /dev/null, so the guest still sees
+     the device but the host no longer tracks guest data on the device.</li>
+     <li>If the value is "requisite", the file is required for
+     booting, but optional on migration.</li>
+   </ul>
+
 <pre>
   ...
   &lt;devices&gt;
     &lt;serial type="file"&gt;
-      &lt;source path="/var/log/vm/vm-serial.log"/&gt;
+      &lt;source path="/var/log/vm/vm-serial.log" startupPolicy="optional"/&gt;
       &lt;target port="1"/&gt;
     &lt;/serial&gt;
   &lt;/devices&gt;
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 745b959..10b3365 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -2817,6 +2817,9 @@
         </optional>
         <optional>
           <attribute name="path"/>
+            <optional>
+              <ref name="startupPolicy"/>
+            </optional>
         </optional>
         <optional>
           <attribute name="host"/>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 10cb7f6..279ff9e 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -6819,6 +6819,7 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
     char *path = NULL;
     char *mode = NULL;
     char *protocol = NULL;
+    char *startupPolicy = NULL;
     int remaining = 0;
 
     while (cur != NULL) {
@@ -6839,6 +6840,9 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
                          !(flags & VIR_DOMAIN_XML_INACTIVE)))
                         path = virXMLPropString(cur, "path");
 
+                    if (startupPolicy == NULL &&
+                        def->type == VIR_DOMAIN_CHR_TYPE_FILE)
+                        startupPolicy = virXMLPropString(cur, "startupPolicy");
                     break;
 
                 case VIR_DOMAIN_CHR_TYPE_UDP:
@@ -6911,6 +6915,13 @@ virDomainChrSourceDefParseXML(virDomainChrSourceDefPtr def,
 
         def->data.file.path = path;
         path = NULL;
+
+        if (startupPolicy) {
+            def->data.file.startupPolicy =
+                virDomainStartupPolicyTypeFromString(startupPolicy);
+            startupPolicy = NULL;
+        }
+ 
         break;
 
     case VIR_DOMAIN_CHR_TYPE_STDIO:
@@ -15014,8 +15025,15 @@ virDomainChrSourceDefFormat(virBufferPtr buf,
         if (def->type != VIR_DOMAIN_CHR_TYPE_PTY ||
             (def->data.file.path &&
              !(flags & VIR_DOMAIN_XML_INACTIVE))) {
-            virBufferEscapeString(buf, "      <source path='%s'/>\n",
-                                  def->data.file.path);
+            virBufferEscapeString(buf, "      <source path='%s'",
+                                   def->data.file.path);
+
+            if (def->data.file.path && def->data.file.startupPolicy) {
+                const char *policy =
+virDomainStartupPolicyTypeToString(def->data.file.startupPolicy);
+                virBufferAsprintf(buf, " startupPolicy='%s'", policy);
+            }
+            virBufferAddLit(buf, "/>\n");
         }
         break;
 
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index f265966..0899556 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1102,6 +1102,7 @@ struct _virDomainChrSourceDef {
         /* no <source> for null, vc, stdio */
         struct {
             char *path;
+            int startupPolicy; /* enum virDomainStartupPolicy */
         } file; /* pty, file, pipe, or device */
         struct {
             char *host;
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index a46d944..35d63d5 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -2511,7 +2511,30 @@ qemuProcessPrepareChardevDevice(virDomainDefPtr def ATTRIBUTE_UNUSED,
         virReportSystemError(errno,
                              _("Unable to pre-create chardev file '%s'"),
                              dev->source.data.file.path);
-        return -1;
+        if (dev->source.data.file.startupPolicy !=
+            VIR_DOMAIN_STARTUP_POLICY_OPTIONAL) {
+            return -1;
+        }
+        VIR_FREE(dev->source.data.file.path);
+        /*
+         *  Change a destination to /dev/null to boot guest OS up
+         *  even if a log disk is broken.
+         */
+        VIR_WARN("Switch the destination to /dev/null");
+        dev->source.data.file.path = strdup("/dev/null");
+
+        if (!(dev->source.data.file.path)) {
+            virReportOOMError();
+            return -1;
+        }
+
+        if ((fd = open(dev->source.data.file.path,
+                       O_CREAT | O_APPEND, S_IRUSR|S_IWUSR)) < 0) {
+            virReportSystemError(errno,
+                                 _("Unable to pre-create chardev file '%s'"),
+                                 dev->source.data.file.path);
+            return -1;
+        }
     }
 
     VIR_FORCE_CLOSE(fd);
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.args b/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.args
new file mode 100644
index 0000000..9ffe8de
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.args
@@ -0,0 +1,9 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/bin/qemu \
+-S -M \
+pc -m 214 -smp 1 -nographic -nodefconfig -nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/test-monitor,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-no-acpi -boot c -usb -hdc /tmp/idedisk.img \
+-chardev file,id=charserial0,path=/tmp/serial.log \
+-device isa-serial,chardev=charserial0,id=serial0 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.xml b/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.xml
new file mode 100644
index 0000000..1aeb82a
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-serial-source-optional.xml
@@ -0,0 +1,35 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <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>
+    <disk type='file' device='disk'>
+      <source file='/tmp/idedisk.img'/>
+      <target dev='hdc' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <serial type='file'>
+      <source path='/tmp/serial.log' startupPolicy='optional'/>
+      <target port='0'/>
+    </serial>
+    <console type='file'>
+      <source path='/tmp/serial.log' startupPolicy='optional'/>
+      <target type='serial' port='0'/>
+    </console>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index 0f96eef..588c922 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -728,6 +728,8 @@ mymain(void)
             QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG);
     DO_TEST("console-compat-chardev",
             QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG);
+    DO_TEST("serial-source-optional",
+            QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG);
 
     DO_TEST("channel-guestfwd",
             QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE, QEMU_CAPS_NODEFCONFIG);
diff --git a/tests/qemuxml2xmltest.c b/tests/qemuxml2xmltest.c
index 77cac3f..9faca1f 100644
--- a/tests/qemuxml2xmltest.c
+++ b/tests/qemuxml2xmltest.c
@@ -234,6 +234,7 @@ mymain(void)
     DO_TEST("console-virtio-many");
     DO_TEST("channel-guestfwd");
     DO_TEST("channel-virtio");
+    DO_TEST("serial-source-optional");
 
     DO_TEST("hostdev-usb-address");
     DO_TEST("hostdev-pci-address");
diff --git a/tests/virt-aa-helper-test b/tests/virt-aa-helper-test
index af91c61..7172fd6 100755
--- a/tests/virt-aa-helper-test
+++ b/tests/virt-aa-helper-test
@@ -255,6 +255,9 @@ testme "0" "disk (empty cdrom)" "-r -u $valid_uuid" "$test_xml"
 sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='file'><source path='$tmpdir/serial.log'/><target port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
 testme "0" "serial" "-r -u $valid_uuid" "$test_xml"
 
+sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='file'><source path='$tmpdir/serial.log' startupPolicy='optional'/><target port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
+testme "0" "serial" "-r -u $valid_uuid" "$test_xml"
+
 sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<serial type='pty'><target port='0'/></serial></devices>,g" "$template_xml" > "$test_xml"
 testme "0" "serial (pty)" "-r -u $valid_uuid" "$test_xml"
 
-- 1.7.1



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