[PATCH 1/2] qemu: add append mode config for serial file

[Oleg Vasilev]

Serial log file contains lots of useful information for debugging
configuration problems. It makes sense to preserve the log in between
restarts, so that one can later figure out what was going on.

Signed-off-by: Oleg Vasilev <oleg.vasilev at virtuozzo.com>
---
 src/qemu/libvirtd_qemu.aug         |  3 +++
 src/qemu/qemu.conf.in              | 10 ++++++++++
 src/qemu/qemu_conf.c               |  4 ++++
 src/qemu/qemu_conf.h               |  2 ++
 src/qemu/qemu_domain.c             | 13 +++++++++++++
 src/qemu/test_libvirtd_qemu.aug.in |  1 +
 6 files changed, 33 insertions(+)

diff --git a/src/qemu/libvirtd_qemu.aug b/src/qemu/libvirtd_qemu.aug
index ed097ea3d9..7f3eec7cfd 100644
--- a/src/qemu/libvirtd_qemu.aug
+++ b/src/qemu/libvirtd_qemu.aug
@@ -147,6 +147,8 @@ module Libvirtd_qemu =
 
    let capability_filters_entry = str_array_entry "capability_filters"
 
+   let serial_file_append_entry = str_entry "serial_file_append"
+
    (* Each entry in the config is one of the following ... *)
    let entry = default_tls_entry
              | vnc_entry
@@ -171,6 +173,7 @@ module Libvirtd_qemu =
              | swtpm_entry
              | capability_filters_entry
              | obsolete_entry
+             | serial_file_append_entry
 
    let comment = [ label "#comment" . del /#[ \t]*/ "# " .  store /([^ \t\n][^\n]*)?/ . del /\n/ "\n" ]
    let empty = [ label "#empty" . eol ]
diff --git a/src/qemu/qemu.conf.in b/src/qemu/qemu.conf.in
index 3895d42514..6b38bbeca0 100644
--- a/src/qemu/qemu.conf.in
+++ b/src/qemu/qemu.conf.in
@@ -968,3 +968,13 @@
 # "full"    -  both QEMU and its helper processes are placed into separate
 #              scheduling group
 #sched_core = "none"
+
+# Default append mode for writing to serial file. QEMU will set the chosen
+# value everytime it processes the config, unless some value is already there.
+#
+# Possible options are:
+# "default" - leave as-is, omit "append=..." from conf, leave for QEMU to decide.
+#             The default for QEMU is the same as with append="off".
+# "on"      - set append value to "on", meaning file won't be truncated on restart
+# "off"     - set append value to "off", file will be cleared on restart
+#serial_file_append = "default"
diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
index ae5bbcd138..bfd93a168f 100644
--- a/src/qemu/qemu_conf.c
+++ b/src/qemu/qemu_conf.c
@@ -288,6 +288,7 @@ virQEMUDriverConfig *virQEMUDriverConfigNew(bool privileged,
         return NULL;
 
     cfg->deprecationBehavior = g_strdup("none");
+    cfg->serialFileAppend = g_strdup("default");
 
     return g_steal_pointer(&cfg);
 }
@@ -376,6 +377,7 @@ static void virQEMUDriverConfigDispose(void *obj)
     g_strfreev(cfg->capabilityfilters);
 
     g_free(cfg->deprecationBehavior);
+    g_free(cfg->serialFileAppend);
 }
 
 
@@ -903,6 +905,8 @@ virQEMUDriverConfigLoadDebugEntry(virQEMUDriverConfig *cfg,
         return -1;
     if (virConfGetValueString(conf, "deprecation_behavior", &cfg->deprecationBehavior) < 0)
         return -1;
+    if (virConfGetValueString(conf, "serial_file_append", &cfg->serialFileAppend) < 0)
+        return -1;
 
     return 0;
 }
diff --git a/src/qemu/qemu_conf.h b/src/qemu/qemu_conf.h
index 8cf2dd2ec5..316200f38d 100644
--- a/src/qemu/qemu_conf.h
+++ b/src/qemu/qemu_conf.h
@@ -229,6 +229,8 @@ struct _virQEMUDriverConfig {
     char *deprecationBehavior;
 
     virQEMUSchedCore schedCore;
+
+    char *serialFileAppend;
 };
 
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(virQEMUDriverConfig, virObjectUnref);
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 8ae458ae45..0d1fe1ffcc 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -37,6 +37,7 @@
 #include "qemu_validate.h"
 #include "qemu_namespace.h"
 #include "viralloc.h"
+#include "virenum.h"
 #include "virlog.h"
 #include "virerror.h"
 #include "viridentity.h"
@@ -5357,6 +5358,8 @@ qemuDomainChrDefPostParse(virDomainChrDef *chr,
                           virQEMUDriver *driver,
                           unsigned int parseFlags)
 {
+    g_autoptr(virQEMUDriverConfig) cfg = virQEMUDriverGetConfig(driver);
+
     /* Historically, isa-serial and the default matched, so in order to
      * maintain backwards compatibility we map them here. The actual default
      * will be picked below based on the architecture and machine type. */
@@ -5428,6 +5431,16 @@ qemuDomainChrDefPostParse(virDomainChrDef *chr,
         }
     }
 
+
+    if (chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_SERIAL &&
+        chr->source &&
+        chr->source->type == VIR_DOMAIN_CHR_TYPE_FILE &&
+        chr->source->data.file.append == VIR_TRISTATE_SWITCH_ABSENT) {
+
+        chr->source->data.file.append =
+            virTristateSwitchTypeFromString(cfg->serialFileAppend);
+    }
+
     return 0;
 }
 
diff --git a/src/qemu/test_libvirtd_qemu.aug.in b/src/qemu/test_libvirtd_qemu.aug.in
index 1dbd692921..d1ca9c8d3d 100644
--- a/src/qemu/test_libvirtd_qemu.aug.in
+++ b/src/qemu/test_libvirtd_qemu.aug.in
@@ -117,3 +117,4 @@ module Test_libvirtd_qemu =
 }
 { "deprecation_behavior" = "none" }
 { "sched_core" = "none" }
+{ "serial_file_append" = "default" }
-- 
2.38.1