[libvirt] [PATCHv2 09/11] qemu_capabilities: Persist QEMU instance over multiple QMP Cmds

[Chris Venteicher]

Commit makes starting a single persistent QEMU instance possible for use
over multiple independent QMP commands without starting and stopping
QEMU for each QMP command or command type.

Commit allows functions outside qemu_capabilities
(ex.  qemuConnectBaselineHypervisorCPU in qemu_driver)
requiring multiple different QMP messages to be sent to QEMU to issue
those requests over a single QMP Command Channel without starting and
stopping QEMU for each independent QMP Command usage.

Commit moves following to global scope so parent function can
maintain QEMU instance over multiple QMP commands / command types:
virQEMUCapsInitQMPCommand
virQEMUCapsInitQMPCommandFree

Commit Introduces virQEMUCapsNewQMPCommandConnection to Start and
connect to QEMU so QMP commands can be performed.

The new reusable function isolates code for starting QEMU and
establishing Monitor connections from code for obtaining capabilities so
that arbitrary QMP commands can be exchanged with QEMU.
---
 src/qemu/qemu_capabilities.c | 61 +++++++++++++++++++++++-------------
 src/qemu/qemu_capabilities.h | 26 +++++++++++++++
 2 files changed, 66 insertions(+), 21 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index f33152ec40..6f8983384a 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -4265,25 +4265,6 @@ virQEMUCapsInitQMPMonitorTCG(virQEMUCapsPtr qemuCaps ATTRIBUTE_UNUSED,
 }
 
 
-typedef struct _virQEMUCapsInitQMPCommand virQEMUCapsInitQMPCommand;
-typedef virQEMUCapsInitQMPCommand *virQEMUCapsInitQMPCommandPtr;
-struct _virQEMUCapsInitQMPCommand {
-    char *binary;
-    uid_t runUid;
-    gid_t runGid;
-    char **qmperr;
-    char *qmperr_internal;
-    char *monarg;
-    char *monpath;
-    char *pidfile;
-    virCommandPtr cmd;
-    qemuMonitorPtr mon;
-    virDomainChrSourceDef config;
-    pid_t pid;
-    virDomainObjPtr vm;
-};
-
-
 static void
 virQEMUCapsInitQMPCommandAbort(virQEMUCapsInitQMPCommandPtr cmd)
 {
@@ -4318,7 +4299,7 @@ virQEMUCapsInitQMPCommandAbort(virQEMUCapsInitQMPCommandPtr cmd)
 }
 
 
-static void
+void
 virQEMUCapsInitQMPCommandFree(virQEMUCapsInitQMPCommandPtr cmd)
 {
     if (!cmd)
@@ -4334,7 +4315,7 @@ virQEMUCapsInitQMPCommandFree(virQEMUCapsInitQMPCommandPtr cmd)
 
 
 static virQEMUCapsInitQMPCommandPtr
-virQEMUCapsInitQMPCommandNew(char *binary,
+virQEMUCapsInitQMPCommandNew(const char *binary,
                              const char *libDir,
                              uid_t runUid,
                              gid_t runGid,
@@ -4475,6 +4456,44 @@ virQEMUCapsInitQMPCommandRun(virQEMUCapsInitQMPCommandPtr cmd,
 }
 
 
+/* Start and connect to QEMU so QMP commands can be performed.
+ */
+virQEMUCapsInitQMPCommandPtr
+virQEMUCapsNewQMPCommandConnection(const char *exec,
+                      const char *libDir, uid_t runUid, gid_t runGid,
+                      bool forceTCG)
+{
+    virQEMUCapsInitQMPCommandPtr cmd = NULL;
+    virQEMUCapsInitQMPCommandPtr rtn_cmd = NULL;
+
+    VIR_DEBUG("exec =%s", NULLSTR(exec));
+
+    /* Allocate and initialize QMPCommand structure */
+    if (!(cmd = virQEMUCapsInitQMPCommandNew(exec, libDir,
+                                             runUid, runGid, NULL)))
+        goto cleanup;
+
+    /* Spawn QEMU and establish connection for QMP commands */
+    if (virQEMUCapsInitQMPCommandRun(cmd, forceTCG) != 0)
+        goto cleanup;
+
+    /* Exit capabilities negotiation mode and enter QEMU command mode
+     * by issuing qmp_capabilities command to QEMU */
+    if (qemuMonitorSetCapabilities(cmd->mon) < 0) {
+        VIR_DEBUG("Failed to set monitor capabilities %s",
+                  virGetLastErrorMessage());
+        goto cleanup;
+    }
+
+    VIR_STEAL_PTR(rtn_cmd, cmd);
+
+ cleanup:
+    virQEMUCapsInitQMPCommandFree(cmd);
+
+    return rtn_cmd;
+}
+
+
 static int
 virQEMUCapsInitQMP(virQEMUCapsPtr qemuCaps,
                    const char *libDir,
diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index d5cd486295..7be636d739 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -490,6 +490,32 @@ typedef enum { /* virQEMUCapsFlags grouping marker for syntax-check */
     QEMU_CAPS_LAST /* this must always be the last item */
 } virQEMUCapsFlags;
 
+typedef struct _virQEMUCapsInitQMPCommand virQEMUCapsInitQMPCommand;
+typedef virQEMUCapsInitQMPCommand *virQEMUCapsInitQMPCommandPtr;
+
+struct _virQEMUCapsInitQMPCommand {
+    char *binary;
+    uid_t runUid;
+    gid_t runGid;
+    char **qmperr;
+    char *qmperr_internal;
+    char *monarg;
+    char *monpath;
+    char *pidfile;
+    virCommandPtr cmd;
+    qemuMonitorPtr mon;
+    virDomainChrSourceDef config;
+    pid_t pid;
+    virDomainObjPtr vm;
+};
+
+virQEMUCapsInitQMPCommandPtr
+virQEMUCapsNewQMPCommandConnection(const char *exec,
+                                   const char *libDir, uid_t runUid, gid_t runGid,
+                                   bool forceTCG);
+
+void virQEMUCapsInitQMPCommandFree(virQEMUCapsInitQMPCommandPtr cmd);
+
 typedef struct _virQEMUCaps virQEMUCaps;
 typedef virQEMUCaps *virQEMUCapsPtr;
 
-- 
2.17.1