[Qemu-devel] [PATCH v4] mc146818rtc: add rtc-reset-reinjection QMP command

["Michael S. Tsirkin" <mst@redhat.com>]

It is necessary to reset RTC interrupt reinjection backlog if
guest time is synchronized via a different mechanism, such as
QGA's guest-set-time command.

Failing to do so causes both corrections to be applied (summed),
resulting in an incorrect guest time.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

Marcelo, is this right?

Changes from v3:
    rebase on top of master
    fixes error code
    drop dead code

 qapi-schema.json       | 12 ++++++++++++
 hw/timer/mc146818rtc.c | 18 ++++++++++++++++++
 monitor.c              |  7 +++++++
 qmp-commands.hx        | 23 +++++++++++++++++++++++
 4 files changed, 60 insertions(+)

diff --git a/qapi-schema.json b/qapi-schema.json
index f490403..a282805 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3288,3 +3288,15 @@
 # Since: 2.1
 ##
 { 'command': 'query-acpi-ospm-status', 'returns': ['ACPIOSTInfo'] }
+
+##
+# @rtc-reset-reinjection
+#
+# This command will reset the RTC interrupt reinjection backlog.
+# Can be used if another mechanism to synchronize guest time
+# is in effect, for example QEMU guest agent's guest-set-time
+# command.
+#
+# Since: 2.1
+##
+{ 'command': 'rtc-reset-reinjection' }
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 1201f90..5bd8710 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -26,6 +26,7 @@
 #include "sysemu/sysemu.h"
 #include "hw/timer/mc146818rtc.h"
 #include "qapi/visitor.h"
+#include "qmp-commands.h"
 
 #ifdef TARGET_I386
 #include "hw/i386/apic.h"
@@ -84,6 +85,7 @@ typedef struct RTCState {
     Notifier clock_reset_notifier;
     LostTickPolicy lost_tick_policy;
     Notifier suspend_notifier;
+    QLIST_ENTRY(RTCState) link;
 } RTCState;
 
 static void rtc_set_time(RTCState *s);
@@ -522,6 +524,20 @@ static void rtc_get_time(RTCState *s, struct tm *tm)
         rtc_from_bcd(s, s->cmos_data[RTC_CENTURY]) * 100 - 1900;
 }
 
+static QLIST_HEAD(, RTCState) rtc_devices =
+    QLIST_HEAD_INITIALIZER(rtc_devices);
+
+#ifdef TARGET_I386
+void qmp_rtc_reset_reinjection(Error **errp)
+{
+    RTCState *s;
+
+    QLIST_FOREACH(s, &rtc_devices, link) {
+        s->irq_coalesced = 0;
+    }
+}
+#endif
+
 static void rtc_set_time(RTCState *s)
 {
     struct tm tm;
@@ -910,6 +926,8 @@ ISADevice *rtc_init(ISABus *bus, int base_year, qemu_irq intercept_irq)
     } else {
         isa_init_irq(isadev, &s->irq, RTC_ISA_IRQ);
     }
+    QLIST_INSERT_HEAD(&rtc_devices, s, link);
+
     return isadev;
 }
 
diff --git a/monitor.c b/monitor.c
index 8c17f89..f7a0206 100644
--- a/monitor.c
+++ b/monitor.c
@@ -5483,3 +5483,10 @@ QemuOptsList qemu_mon_opts = {
         { /* end of list */ }
     },
 };
+
+#ifndef TARGET_I386
+void qmp_rtc_reset_reinjection(Error **errp)
+{
+    error_set(errp, QERR_FEATURE_DISABLED, "rtc-reset-reinjection");
+}
+#endif
diff --git a/qmp-commands.hx b/qmp-commands.hx
index e4a1c80..17c09de 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3661,3 +3661,26 @@ Example:
                  { "slot": "3", "slot-type": "DIMM", "source": 0, "status": 0}
    ]}
 EQMP
+
+#if defined TARGET_I386
+    {
+        .name       = "rtc-reset-reinjection",
+        .args_type  = "",
+        .mhandler.cmd_new = qmp_marshal_input_rtc_reset_reinjection,
+    },
+#endif
+
+SQMP
+rtc-reset-reinjection
+---------------------
+
+Reset the RTC interrupt reinjection backlog.
+
+Arguments: None.
+
+Example:
+
+-> { "execute": "rtc-reset-reinjection" }
+<- { "return": {} }
+
+EQMP
-- 
MST