[libvirt] [PATCH RFC] libxl: set serial source path for console type=serial

[Joao Martins]

Guests use a <console /> (and sometimes <serial /> pair) to represent
the console. On the callback that is called when console is brought up
(NB: before domain starts), we fill the path of the console element with
the appropriate "/dev/pts/X". For PV guests it all works fine, although
for HVM guests it doesn't. Consequently we end up seeing erronous
behaviour on HVM guests where console path is not displayed on the XML
but still can be accessed with virDomainOpenConsole after booting guest.
Consumers of this XML (e.g. Openstack) also won't be able to use the
console path. Finally, the path set in consoles array won't persist
across daemon reboots, thus rendering admins/users with no access to
console with a message such as:

"error: operation failed: PTY device is not yet assigned"

This is because: for HVM guests, DefFormatInternal will ignore the
console element and instead write it with the content of the serial
element for target type = serial which isn't touched in our
libxlConsoleCallback. To address that we introduce a new helper routine
libxlConsoleSetSourcePath() that sets the source path and thus also
handling this case. That is by setting the source path on with serial
element akin to the one indexed by console "port". This way we keep
similar behaviour for PV and HVM guests.

Signed-off-by: Joao Martins <joao.m.martins at oracle.com>
---
 src/libxl/libxl_domain.c | 35 +++++++++++++++++++++++++++++++----
 1 file changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
index 221af87..4a46143 100644
--- a/src/libxl/libxl_domain.c
+++ b/src/libxl/libxl_domain.c
@@ -955,6 +955,35 @@ libxlNetworkPrepareDevices(virDomainDefPtr def)
     return 0;
 }
 
+static int
+libxlConsoleSetSourcePath(virDomainDefPtr def, virDomainChrDefPtr console,
+                          char *path)
+{
+    int ret = -1;
+    size_t i;
+
+    if (!path || path[0] == '\0')
+        return ret;
+
+    if (VIR_STRDUP(console->source.data.file.path, path) < 0)
+        return ret;
+
+    if (console->targetType != VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL)
+        return 0;
+
+    for (i = 0; i < def->nserials; i++) {
+        virDomainChrDefPtr serial = def->serials[i];
+
+        if (serial->target.port == console->target.port &&
+            VIR_STRDUP(serial->source.data.file.path, path) >= 0) {
+            ret = 0;
+            break;
+        }
+    }
+
+    return ret;
+}
+
 static void
 libxlConsoleCallback(libxl_ctx *ctx, libxl_event *ev, void *for_callback)
 {
@@ -977,10 +1006,8 @@ libxlConsoleCallback(libxl_ctx *ctx, libxl_event *ev, void *for_callback)
                                         &console);
             if (!ret) {
                 VIR_FREE(chr->source.data.file.path);
-                if (console && console[0] != '\0') {
-                    ignore_value(VIR_STRDUP(chr->source.data.file.path,
-                                            console));
-                }
+                if (libxlConsoleSetSourcePath(vm->def, chr, console) < 0)
+                    VIR_WARN("Failed to set console source path");
             }
             VIR_FREE(console);
         }
-- 
2.1.4