[1/3] mc146818rtc: add rtc-reset-reinjection QMP command

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>

---
 hw/timer/mc146818rtc.c |   22 ++++++++++++++++++++++
 qapi-schema.json       |   12 ++++++++++++
 qmp-commands.hx        |   23 +++++++++++++++++++++++
 3 files changed, 57 insertions(+)

On Wed, Jun 04, 2014 at 02:52:01PM -0300, mtosatti@redhat.com wrote:
> 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>
> 
> ---
>  hw/timer/mc146818rtc.c |   22 ++++++++++++++++++++++
>  qapi-schema.json       |   12 ++++++++++++
>  qmp-commands.hx        |   23 +++++++++++++++++++++++
>  3 files changed, 57 insertions(+)
> 
> Index: qemu/hw/timer/mc146818rtc.c
> ===================================================================
> --- qemu.orig/hw/timer/mc146818rtc.c	2014-06-02 23:14:09.570443599 -0300
> +++ qemu/hw/timer/mc146818rtc.c	2014-06-02 23:14:11.707436729 -0300
> @@ -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 +85,9 @@
>      Notifier clock_reset_notifier;
>      LostTickPolicy lost_tick_policy;
>      Notifier suspend_notifier;
> +#ifdef TARGET_I386
> +    QLIST_ENTRY(RTCState) link;
> +#endif

Could we avoid these ifdefs?
I'd rather maintain the link unconditionally,
even if it's unused except on x86.

>  } RTCState;
>  
>  static void rtc_set_time(RTCState *s);
> @@ -522,6 +526,20 @@
>          rtc_from_bcd(s, s->cmos_data[RTC_CENTURY]) * 100 - 1900;
>  }
>  
> +#ifdef TARGET_I386
> +static QLIST_HEAD(, RTCState) rtc_devices =
> +    QLIST_HEAD_INITIALIZER(rtc_devices);
> +
> +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;
> @@ -911,6 +929,10 @@
>      } else {
>          isa_init_irq(isadev, &s->irq, RTC_ISA_IRQ);
>      }
> +#ifdef TARGET_I386
> +    QLIST_INSERT_HEAD(&rtc_devices, s, link);
> +#endif
> +
>      return isadev;
>  }
>  
> Index: qemu/qapi-schema.json
> ===================================================================
> --- qemu.orig/qapi-schema.json	2014-06-02 23:14:09.570443599 -0300
> +++ qemu/qapi-schema.json	2014-06-02 23:14:11.709436722 -0300
> @@ -4722,3 +4722,15 @@
>                'btn'     : 'InputBtnEvent',
>                'rel'     : 'InputMoveEvent',
>                'abs'     : 'InputMoveEvent' } }
> +
> +##
> +# @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' }
> Index: qemu/qmp-commands.hx
> ===================================================================
> --- qemu.orig/qmp-commands.hx	2014-06-02 23:14:09.570443599 -0300
> +++ qemu/qmp-commands.hx	2014-06-02 23:14:11.710436719 -0300
> @@ -3572,3 +3572,26 @@
>                     } } ] }
>  
>  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
> 
>

On 06/04/2014 11:52 AM, mtosatti@redhat.com wrote:
> 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>
> 
> ---
>  hw/timer/mc146818rtc.c |   22 ++++++++++++++++++++++
>  qapi-schema.json       |   12 ++++++++++++
>  qmp-commands.hx        |   23 +++++++++++++++++++++++
>  3 files changed, 57 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>