qemu: add support for dump-guest-core option

The "dump-guest-core' option is new option for the machine type
(-machine pc,dump-guest-core) that controls whether the guest memory
will be marked as dumpable.

While testing this, I've found out that the value for the '-M' options
is not parsed correctly when additional parameters are used. However,
when '-machine' is used for the same options, it gets parsed as
expected. That's why this patch also modifies the parsing and creating
of the command line, so both '-M' and '-machine' are recognized. In
QEMU's help there is only mention of the 'machine parameter now with
no sign of the older '-M'.

src/qemu/qemu_capabilities.c

@@ -182,6 +182,7 @@ VIR_ENUM_IMPL(qemuCaps, QEMU_CAPS_LAST,
               "seccomp-sandbox",
 
               "reboot-timeout", /* 110 */
+              "dump-guest-core",
     );
 
 struct _qemuCaps {
@@ -1243,6 +1244,9 @@ qemuCapsComputeCmdFlags(const char *help,
     if (strstr(help, "-no-shutdown") && (version < 14000 || version > 15000))
         qemuCapsSet(caps, QEMU_CAPS_NO_SHUTDOWN);
 
+    if (strstr(help, "dump-guest-core=on|off"))
+        qemuCapsSet(caps, QEMU_CAPS_DUMP_GUEST_CORE);
+
     /*
      * Handling of -incoming arg with varying features
      *  -incoming tcp    (kvm >= 79, qemu >= 0.10.0)

src/qemu/qemu_capabilities.h

@@ -146,6 +146,7 @@ enum qemuCapsFlags {
     QEMU_CAPS_SCSI_DISK_WWN      = 108, /* Is scsi-disk.wwn available? */
     QEMU_CAPS_SECCOMP_SANDBOX    = 109, /* -sandbox */
     QEMU_CAPS_REBOOT_TIMEOUT     = 110, /* -boot reboot-timeout */
+    QEMU_CAPS_DUMP_GUEST_CORE    = 111, /* dump-guest-core-parameter */
 
     QEMU_CAPS_LAST,                   /* this must always be the last item */
 };

src/qemu/qemu_command.c

@@ -4306,6 +4306,44 @@ no_memory:
     goto cleanup;
 }
 
+static int
+qemuBuildMachineArgStr(virCommandPtr cmd,
+                       const virDomainDefPtr def,
+                       qemuCapsPtr caps)
+{
+    /* This should *never* be NULL, since we always provide
+     * a machine in the capabilities data for QEMU. So this
+     * check is just here as a safety in case the unexpected
+     * happens */
+    if (!def->os.machine)
+        return 0;
+
+    if (!def->mem.dump_core) {
+        /* if no parameter to the machine type is needed, we still use
+         * '-M' to keep the most of the compatibility with older versions.
+         */
+        virCommandAddArgList(cmd, "-M", def->os.machine, NULL);
+    } else {
+        if (!qemuCapsGet(caps, QEMU_CAPS_DUMP_GUEST_CORE)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           "%s", _("dump-guest-core is not available "
+                                   " with this QEMU binary"));
+            return -1;
+        }
+
+        /* However, in case there is a parameter to be added, we need to
+         * use the "-machine" parameter because qemu is not parsing the
+         * "-M" correctly */
+        virCommandAddArg(cmd, "-machine");
+        virCommandAddArgFormat(cmd,
+                               "%s,dump-guest-core=%s",
+                               def->os.machine,
+                               virDomainMemDumpTypeToString(def->mem.dump_core));
+    }
+
+    return 0;
+}
+
 static char *
 qemuBuildSmpArgStr(const virDomainDefPtr def,
                    qemuCapsPtr caps)
@@ -4498,12 +4536,8 @@ qemuBuildCommandLine(virConnectPtr conn,
     }
     virCommandAddArg(cmd, "-S"); /* freeze CPU */
 
-    /* This should *never* be NULL, since we always provide
+    if (qemuBuildMachineArgStr(cmd, def, caps) < 0)
-     * a machine in the capabilities data for QEMU. So this
+        goto error;
-     * check is just here as a safety in case the unexpected
-     * happens */
-    if (def->os.machine)
-        virCommandAddArgList(cmd, "-M", def->os.machine, NULL);
 
     if (qemuBuildCpuArgStr(driver, def, emulator, caps,
                            &ut, &cpu, &hasHwVirt, !!migrateFrom) < 0)
@@ -8323,10 +8357,38 @@ virDomainDefPtr qemuParseCommandLine(virCapsPtr caps,
             }
             if (STREQ(def->name, ""))
                 VIR_FREE(def->name);
-        } else if (STREQ(arg, "-M")) {
+        } else if (STREQ(arg, "-M") ||
+                   STREQ(arg, "-machine")) {
+            char *params;
             WANT_VALUE();
-            if (!(def->os.machine = strdup(val)))
+            params = strchr(val, ',');
-                goto no_memory;
+            if (params == NULL) {
+                if (!(def->os.machine = strdup(val)))
+                    goto no_memory;
+            } else {
+                if (!(def->os.machine = strndup(val, params - val)))
+                    goto no_memory;
+
+                while(params++) {
+                    /* prepared for more "-machine" parameters */
+                    char *tmp = params;
+                    params = strchr(params, ',');
+
+                    if (STRPREFIX(tmp, "dump-guest-core=")) {
+                        tmp += strlen("dump-guest-core=");
+                        if (params) {
+                            tmp = strndup(tmp, params - tmp);
+                            if (tmp == NULL)
+                                goto no_memory;
+                        }
+                        def->mem.dump_core = virDomainMemDumpTypeFromString(tmp);
+                        if (def->mem.dump_core <= 0)
+                            def->mem.dump_core = VIR_DOMAIN_MEM_DUMP_DEFAULT;
+                        if (params)
+                            VIR_FREE(tmp);
+                    }
+                }
+            }
         } else if (STREQ(arg, "-serial")) {
             WANT_VALUE();
             if (STRNEQ(val, "none")) {

tests/qemuhelptest.c

@@ -846,7 +846,8 @@ mymain(void)
             QEMU_CAPS_VIRTIO_SCSI_PCI,
             QEMU_CAPS_BLOCKIO,
             QEMU_CAPS_SCSI_DISK_WWN,
-            QEMU_CAPS_SECCOMP_SANDBOX);
+            QEMU_CAPS_SECCOMP_SANDBOX,
+            QEMU_CAPS_DUMP_GUEST_CORE);
 
     return ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE;
 }