qemu: add vmcoreinfo support

Starting from qemu 2.11, the `-device vmcoreinfo` will create a fw_cfg
entry for a guest to store dump details, necessary to process kernel
dump with KASLR enabled and providing additional kernel details.

In essence, it is similar to -fw_cfg name=etc/vmcoreinfo,file=X but in
this case it is not backed by a file, but collected by QEMU itself.

Since the device is a singleton and shouldn't use additional hardware
resources, it is presented as a <feature> element in the libvirt
domain XML.

The device is arm/x86 only for now (targets that support fw_cfg+dma).

Related to:
https://bugzilla.redhat.com/show_bug.cgi?id=1395248

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

docs/formatdomain.html.in

@@ -1951,6 +1951,10 @@
           the attribute is not defined, the hypervisor default will be used.
           <span class="since">Since 3.10.0</span> (QEMU/KVM only)
       </dd>
+      <dt><code>vmcoreinfo</code></dt>
+      <dd>Enable QEMU vmcoreinfo device to let the guest kernel save debug
+          details. <span class="since">Since 3.10.0</span> (QEMU only)
+      </dd>
     </dl>
 
     <h3><a id="elementsTime">Time keeping</a></h3>

docs/schemas/domaincommon.rng

@@ -4739,6 +4739,9 @@
           <optional>
             <ref name="hpt"/>
           </optional>
+          <optional>
+            <ref name="vmcoreinfo"/>
+          </optional>
         </interleave>
       </element>
     </optional>
@@ -4939,6 +4942,12 @@
     </element>
   </define>
 
+  <define name="vmcoreinfo">
+    <element name="vmcoreinfo">
+      <empty/>
+    </element>
+  </define>
+
   <define name="address">
     <element name="address">
       <choice>

src/conf/domain_conf.c

@@ -151,6 +151,7 @@ VIR_ENUM_IMPL(virDomainFeature, VIR_DOMAIN_FEATURE_LAST,
               "smm",
               "ioapic",
               "hpt",
+              "vmcoreinfo",
 );
 
 VIR_ENUM_IMPL(virDomainCapabilitiesPolicy, VIR_DOMAIN_CAPABILITIES_POLICY_LAST,
@@ -18719,6 +18720,7 @@ virDomainDefParseXML(xmlDocPtr xml,
         case VIR_DOMAIN_FEATURE_VIRIDIAN:
         case VIR_DOMAIN_FEATURE_PRIVNET:
         case VIR_DOMAIN_FEATURE_HYPERV:
+        case VIR_DOMAIN_FEATURE_VMCOREINFO:
         case VIR_DOMAIN_FEATURE_KVM:
             def->features[val] = VIR_TRISTATE_SWITCH_ON;
             break;
@@ -26089,6 +26091,7 @@ virDomainDefFormatInternal(virDomainDefPtr def,
             case VIR_DOMAIN_FEATURE_ACPI:
             case VIR_DOMAIN_FEATURE_PAE:
             case VIR_DOMAIN_FEATURE_VIRIDIAN:
+            case VIR_DOMAIN_FEATURE_VMCOREINFO:
             case VIR_DOMAIN_FEATURE_PRIVNET:
                 switch ((virTristateSwitch) def->features[i]) {
                 case VIR_TRISTATE_SWITCH_ABSENT:

src/conf/domain_conf.h

@@ -1724,6 +1724,7 @@ typedef enum {
     VIR_DOMAIN_FEATURE_SMM,
     VIR_DOMAIN_FEATURE_IOAPIC,
     VIR_DOMAIN_FEATURE_HPT,
+    VIR_DOMAIN_FEATURE_VMCOREINFO,
 
     VIR_DOMAIN_FEATURE_LAST
 } virDomainFeature;

src/qemu/qemu_capabilities.c

@@ -444,6 +444,7 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAST,
               "vxhs",
               "virtio-blk.num-queues",
               "machine.pseries.resize-hpt",
+              "vmcoreinfo",
     );
 
 
@@ -1671,6 +1672,7 @@ struct virQEMUCapsStringFlags virQEMUCapsObjectTypes[] = {
     { "pcie-root-port", QEMU_CAPS_DEVICE_PCIE_ROOT_PORT },
     { "qemu-xhci", QEMU_CAPS_DEVICE_QEMU_XHCI },
     { "spapr-pci-host-bridge", QEMU_CAPS_DEVICE_SPAPR_PCI_HOST_BRIDGE },
+    { "vmcoreinfo", QEMU_CAPS_DEVICE_VMCOREINFO },
 };
 
 static struct virQEMUCapsStringFlags virQEMUCapsObjectPropsVirtioBalloon[] = {

src/qemu/qemu_capabilities.h

@@ -430,6 +430,7 @@ typedef enum {
     QEMU_CAPS_VXHS, /* -drive file.driver=vxhs via query-qmp-schema */
     QEMU_CAPS_VIRTIO_BLK_NUM_QUEUES, /* virtio-blk-*.num-queues */
     QEMU_CAPS_MACHINE_PSERIES_RESIZE_HPT, /* -machine pseries,resize-hpt */
+    QEMU_CAPS_DEVICE_VMCOREINFO, /* -device vmcoreinfo */
 
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;

src/qemu/qemu_command.c

@@ -9710,6 +9710,28 @@ qemuBuildTPMCommandLine(virCommandPtr cmd,
 }
 
 
+static int
+qemuBuildVMCoreInfoCommandLine(virCommandPtr cmd,
+                               const virDomainDef *def,
+                               virQEMUCapsPtr qemuCaps)
+{
+    virTristateSwitch vmci = def->features[VIR_DOMAIN_FEATURE_VMCOREINFO];
+
+    if (vmci != VIR_TRISTATE_SWITCH_ON)
+        return 0;
+
+    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_VMCOREINFO)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("vmcoreinfo is not available "
+                         "with this QEMU binary"));
+        return -1;
+    }
+
+    virCommandAddArgList(cmd, "-device", "vmcoreinfo", NULL);
+    return 0;
+}
+
+
 static int
 qemuBuildPanicCommandLine(virCommandPtr cmd,
                           const virDomainDef *def,
@@ -10129,6 +10151,9 @@ qemuBuildCommandLine(virQEMUDriverPtr driver,
     if (qemuBuildNVRAMCommandLine(cmd, def, qemuCaps) < 0)
         goto error;
 
+    if (qemuBuildVMCoreInfoCommandLine(cmd, def, qemuCaps) < 0)
+        goto error;
+
     if (snapshot)
         virCommandAddArgList(cmd, "-loadvm", snapshot->def->name, NULL);
 

tests/qemuxml2argvdata/qemuxml2argv-vmcoreinfo.args

@@ -0,0 +1,25 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/home/test \
+USER=test \
+LOGNAME=test \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-i686 \
+-name QEMUGuest1 \
+-S \
+-M pc \
+-m 214 \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-nographic \
+-nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/lib/domain--1-QEMUGuest1/monitor.sock,\
+server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline \
+-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 \
+-device vmcoreinfo

tests/qemuxml2argvdata/qemuxml2argv-vmcoreinfo.xml

@@ -0,0 +1,28 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <features>
+    <vmcoreinfo/>
+  </features>
+  <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='ide' index='0'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -2822,6 +2822,7 @@ mymain(void)
     DO_TEST_PARSE_ERROR("cpu-cache-emulate-l2", QEMU_CAPS_KVM);
     DO_TEST_PARSE_ERROR("cpu-cache-passthrough3", QEMU_CAPS_KVM);
     DO_TEST_PARSE_ERROR("cpu-cache-passthrough-l3", QEMU_CAPS_KVM);
+    DO_TEST("vmcoreinfo", QEMU_CAPS_DEVICE_VMCOREINFO);
 
     DO_TEST("user-aliases", QEMU_CAPS_KVM, QEMU_CAPS_DEVICE_CIRRUS_VGA,
             QEMU_CAPS_OBJECT_MEMORY_FILE, QEMU_CAPS_PIIX_DISABLE_S3,

tests/qemuxml2xmloutdata/qemuxml2xmlout-vmcoreinfo.xml

@@ -0,0 +1,38 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <features>
+    <vmcoreinfo/>
+  </features>
+  <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='ide' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='usb' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
+    </memballoon>
+  </devices>
+</domain>

tests/qemuxml2xmltest.c

@@ -1265,6 +1265,7 @@ mymain(void)
     DO_TEST("cpu-check-default-none2", NONE);
     DO_TEST("cpu-check-default-partial", NONE);
     DO_TEST("cpu-check-default-partial2", NONE);
+    DO_TEST("vmcoreinfo", NONE);
 
     DO_TEST("smartcard-host", NONE);
     DO_TEST("smartcard-host-certificates", NONE);