[libvirt] [PATCH] qemu_monitor_json: add support to search QOM device path by device alias

[Martin Kletzander]

On Mon, Jul 25, 2016 at 02:41:01PM +0200, Pavel Hrdina wrote:
>Commit ce745914 introduced detection of actual video ram sizes to fix migration
>if QEMU decide to modify the values provided by libvirt.  This works perfectly
>for domains with number of video devices up to two.
>
>If there are more than two video devices in the guest all the secondary devices
>in the XML will have the same memory values.  This is because our current code
>search for QOM device path only by the device type name and all the secondary
>video devices has the same name "qxl".
>
>This patch introduces a new search function that will try to search a QOM device
>path using also device's alias if the alias is available. After that it will
>fallback to the old recursive code if the alias search found no results.
>
>Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1358728
>
>Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
>---
> src/qemu/qemu_monitor.c      | 11 ++++---
> src/qemu/qemu_monitor_json.c | 74 ++++++++++++++++++++++++++++++++++++++------
> src/qemu/qemu_monitor_json.h |  3 +-
> 3 files changed, 74 insertions(+), 14 deletions(-)
>
>diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
>index 098e654..1fac4de 100644
>--- a/src/qemu/qemu_monitor.c
>+++ b/src/qemu/qemu_monitor.c
>@@ -1084,10 +1084,11 @@ qemuMonitorInitBalloonObjectPath(qemuMonitorPtr mon)
>     }
>     mon->ballooninit = true;
>
>-    flp_ret = qemuMonitorJSONFindLinkPath(mon, "virtio-balloon-pci", &path);
>+    flp_ret = qemuMonitorJSONFindLinkPath(mon, "virtio-balloon-pci", NULL, &path);
>     if (flp_ret == -2) {
>         /* pci object was not found retry search for ccw object */
>-        if (qemuMonitorJSONFindLinkPath(mon, "virtio-balloon-ccw", &path) < 0)
>+        if (qemuMonitorJSONFindLinkPath(mon, "virtio-balloon-ccw",
>+                                        NULL, &path) < 0)

We could pass the balloon alias here through all the functions, right?
Although it will be literally 'balloon0' every single time there is any,
so maybe we could use that.

>diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
>index bb426dc..5d24e26 100644
>--- a/src/qemu/qemu_monitor_json.c
>+++ b/src/qemu/qemu_monitor_json.c
>@@ -6810,7 +6810,55 @@ qemuMonitorJSONGetMemoryDeviceInfo(qemuMonitorPtr mon,
>
>
> /**
>- * Recursively search for a QOM object link.
>+ * Search for a QOM object link by alias and name.
>+ *
>+ * For @alias and @name, this function tries to find QOM object named @name
>+ * with id @alias in /machine/peripheral.
>+ *
>+ * Returns:
>+ *   0  - Found
>+ *  -1  - Error - bail out
>+ *  -2  - Not found
>+ */
>+static int
>+qemuMonitorJSONFindObjectPathByAlias(qemuMonitorPtr mon,
>+                                     const char *name,
>+                                     const char *alias,
>+                                     char **path)
>+{
>+    qemuMonitorJSONListPathPtr *paths = NULL;
>+    char *child = NULL;
>+    int npaths;
>+    int ret = -1;
>+    size_t i;
>+
>+    npaths = qemuMonitorJSONGetObjectListPaths(mon, "/machine/peripheral", &paths);
>+    if (npaths < 0)
>+        return -1;
>+
>+    if (virAsprintf(&child, "child<%s>", name) < 0)
>+        return -1;
>+
>+    for (i = 0; i < npaths; i++) {
>+        if (STREQ(paths[i]->name, alias) && STREQ(paths[i]->type, child)) {
>+            if (virAsprintf(path, "/machine/peripheral/%s", alias) < 0)
>+                goto cleanup;
>+
>+            ret = 0;
>+            goto cleanup;
>+        }
>+    }
>+
>+    ret = -2;
>+
>+ cleanup:
>+    VIR_FREE(child);
>+    return ret;
>+}
>+

You are missing qemuMonitorJSONListPathFree() here (and also the returns
above need to be fixed).

ACK with that fixed.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: Digital signature
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20160725/785ff242/attachment-0001.sig>