[PATCH 1/2] domain: add tsc.on_reboot element

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

Some versions of Windows hang on reboot if their TSC value is greater
than 2^54.  The workaround is to reset the TSC to a small value.  Add
to the domain configuration an attribute for this.  It can be used
by QEMU and in principle also by ESXi, which has a property called
monitor_control.enable_softResetClearTSC as well.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 docs/formatdomain.rst             |  4 ++++
 src/conf/domain_conf.c            | 22 ++++++++++++++++++++++
 src/conf/domain_conf.h            | 10 ++++++++++
 src/conf/schemas/domaincommon.rng |  9 +++++++++
 4 files changed, 45 insertions(+)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index d188de4858..c9319e42ac 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -2241,6 +2241,10 @@ Windows, however, expects it to be in so called 'localtime'.
    ``frequency``
       The ``frequency`` attribute is an unsigned integer specifying the
       frequency at which ``name="tsc"`` runs.
+   ``on_reboot``
+      The ``on_reboot`` attribute controls how the ``name="tsc"`` timer behaves
+      when the VM is reset, and can be "default", "clear" or "keep". The reset
+      behavior of other timers is hardcoded, and depends on the type of timer.
    ``mode``
       The ``mode`` attribute controls how the ``name="tsc"`` timer is managed,
       and can be "auto", "native", "emulate", "paravirt", or "smpsafe". Other
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 153954a0b0..1893b8bbca 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -1217,6 +1217,13 @@ VIR_ENUM_IMPL(virDomainTimerMode,
               "smpsafe",
 );
 
+VIR_ENUM_IMPL(virDomainTimerRebootMode,
+              VIR_DOMAIN_TIMER_REBOOT_MODE_LAST,
+              "default",
+              "keep",
+              "clear",
+);
+
 VIR_ENUM_IMPL(virDomainStartupPolicy,
               VIR_DOMAIN_STARTUP_POLICY_LAST,
               "default",
@@ -12022,6 +12029,7 @@ virDomainTimerDefParseXML(xmlNodePtr node,
     g_autofree char *tickpolicy = NULL;
     g_autofree char *track = NULL;
     g_autofree char *mode = NULL;
+    g_autofree char *reboot = NULL;
 
     def = g_new0(virDomainTimerDef, 1);
 
@@ -12080,6 +12088,15 @@ virDomainTimerDefParseXML(xmlNodePtr node,
         }
     }
 
+    reboot = virXMLPropString(node, "on_reboot");
+    if (reboot != NULL) {
+        if ((def->reboot = virDomainTimerRebootModeTypeFromString(reboot)) <= 0) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("unknown timer reboot mode '%s'"), reboot);
+            goto error;
+        }
+    }
+
     catchup = virXPathNode("./catchup", ctxt);
     if (catchup != NULL) {
         ret = virXPathULong("string(./catchup/@threshold)", ctxt,
@@ -26151,6 +26168,11 @@ virDomainTimerDefFormat(virBuffer *buf,
             virBufferAsprintf(&timerAttr, " mode='%s'",
                               virDomainTimerModeTypeToString(def->mode));
         }
+
+        if (def->reboot) {
+            virBufferAsprintf(&timerAttr, " on_reboot='%s'",
+                              virDomainTimerRebootModeTypeToString(def->mode));
+        }
     }
 
     if (def->catchup.threshold > 0)
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index b69abfa270..3618410f6c 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2408,6 +2408,14 @@ typedef enum {
     VIR_DOMAIN_TIMER_MODE_LAST
 } virDomainTimerModeType;
 
+typedef enum {
+    VIR_DOMAIN_TIMER_REBOOT_MODE_DEFAULT = 0,
+    VIR_DOMAIN_TIMER_REBOOT_MODE_KEEP,
+    VIR_DOMAIN_TIMER_REBOOT_MODE_CLEAR,
+
+    VIR_DOMAIN_TIMER_REBOOT_MODE_LAST
+} virDomainTimerRebootModeType;
+
 typedef enum {
     VIR_DOMAIN_CPU_PLACEMENT_MODE_STATIC = 0,
     VIR_DOMAIN_CPU_PLACEMENT_MODE_AUTO,
@@ -2439,6 +2447,7 @@ struct _virDomainTimerDef {
     /* frequency & mode are only valid for name='tsc' */
     unsigned long long frequency; /* in Hz, unspecified = 0 */
     int mode;   /* enum virDomainTimerModeType */
+    int reboot;   /* enum virDomainTimerRebootModeType */
 };
 
 typedef enum {
@@ -4032,6 +4041,7 @@ VIR_ENUM_DECL(virDomainClockBasis);
 VIR_ENUM_DECL(virDomainTimerName);
 VIR_ENUM_DECL(virDomainTimerTrack);
 VIR_ENUM_DECL(virDomainTimerTickpolicy);
+VIR_ENUM_DECL(virDomainTimerRebootMode);
 VIR_ENUM_DECL(virDomainTimerMode);
 VIR_ENUM_DECL(virDomainCpuPlacementMode);
 
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index 9c1b64a644..10d0404889 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -1285,6 +1285,15 @@
               <ref name="unsignedLong"/>
             </attribute>
           </optional>
+          <optional>
+            <attribute name="on_reboot">
+              <choice>
+                <value>default</value>
+                <value>clear</value>
+                <value>keep</value>
+              </choice>
+            </attribute>
+          </optional>
           <optional>
             <attribute name="mode">
               <choice>
-- 
2.35.1