[PATCH] qemu_alias: Fix backcompat console alias generation

[Michal Privoznik]

We have this crazy backwards compatibility when it comes to
serial and console devices. Basically, in same cases the very
first <console/> is just an alias to the very first <serial/>
device. This is to be seen at various places:

1) virDomainDefFormatInternalSetRootName() - when generating
   domain XML, the <console/> configuration is basically ignored
   and corresponding <serial/> config is formatted,

2) virDomainDefAddConsoleCompat() - which adds a copy of
   <serial/> or <console/> into virDomainDef in post parse.

And when talking to QEMU we need a special handling too, because
while <serial/> is generated on the cmd line, the <console/> is
not. And in a lot of place we get it right. Except for generating
device aliases. On domain startup the 'expected' happens and
devices get "serial0" and "console0" aliases, correspondingly.
This ends up in the status XML too. But due to aforementioned
trick when formatting domain XML, "serial0" ends up in both
'virsh dumpxml' and the status XML. But internally, both devices
have different alias. Therefore, detaching the device using
<console/> fails as qemuDomainDetachDeviceChr() tries to detach
"console0".

After the daemon is restarted and status XML is parsed, then
everything works suddenly. This is because in the status XML both
devices have the same alias.

Let's generate correct alias from the beginning.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2156300
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_alias.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/src/qemu/qemu_alias.c b/src/qemu/qemu_alias.c
index a9809797d5..05d25da93d 100644
--- a/src/qemu/qemu_alias.c
+++ b/src/qemu/qemu_alias.c
@@ -90,6 +90,18 @@ qemuAssignDeviceChrAlias(virDomainDef *def,
     if (chr->info.alias)
         return 0;
 
+    /* Some crazy backcompat for consoles. Look into
+     * virDomainDefAddConsoleCompat() for more explanation. */
+    if (chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE &&
+        chr->targetType == VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL &&
+        def->os.type == VIR_DOMAIN_OSTYPE_HVM &&
+        def->consoles[0] == chr &&
+        def->nserials &&
+        def->serials[0]->info.alias) {
+        chr->info.alias = g_strdup(def->serials[0]->info.alias);
+        return 0;
+    }
+
     switch ((virDomainChrDeviceType)chr->deviceType) {
     case VIR_DOMAIN_CHR_DEVICE_TYPE_PARALLEL:
         prefix = "parallel";
-- 
2.39.2