Re: [Qemu-devel] [PATCH] RTC: enable lost_tick_policy=slew as default (v2)

[Anthony Liguori <aliguori@us.ibm.com>]

Marcelo Tosatti <mtosatti@redhat.com> writes:

> On Thu, Mar 07, 2013 at 09:25:17AM +0100, Paolo Bonzini wrote:
>> Il 12/12/2012 22:36, Marcelo Tosatti ha scritto:
>> > 
>> > RTC interrupt reinjection has no known negative effect. Lack of
>> > RTC interrupt reinjection, though, has negative effects: time drift
>> > for Windows guests which use it as a timer source.
>> > 
>> > Based on that, enable lost_tick_policy=slew option as default.
>> > 
>> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>> > 
>> > v2: do not change default for older machines types (Paolo Bonzini)
>> > 
>> > diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
>> > index c79fca7..c9e007d 100644
>> > --- a/hw/mc146818rtc.c
>> > +++ b/hw/mc146818rtc.c
>> > @@ -884,7 +884,7 @@ ISADevice *rtc_init(ISABus *bus, int base_year, qemu_irq intercept_irq)
>> >  static Property mc146818rtc_properties[] = {
>> >      DEFINE_PROP_INT32("base_year", RTCState, base_year, 1980),
>> >      DEFINE_PROP_LOSTTICKPOLICY("lost_tick_policy", RTCState,
>> > -                               lost_tick_policy, LOST_TICK_DISCARD),
>> > +                               lost_tick_policy, LOST_TICK_SLEW),
>> >      DEFINE_PROP_END_OF_LIST(),
>> >  };
>> >  
>> > diff --git a/hw/pc_piix.c b/hw/pc_piix.c
>> > index 19e342a..475bb4c 100644
>> > --- a/hw/pc_piix.c
>> > +++ b/hw/pc_piix.c
>> > @@ -295,6 +295,10 @@ static QEMUMachine pc_machine_v1_4 = {
>> >              .driver   = "usb-tablet",\
>> >              .property = "usb_version",\
>> >              .value    = stringify(1),\
>> > +        },{\
>> > +            .driver   = "mc146818rtc",\
>> > +            .property = "lost_tick_policy",\
>> > +            .value    = "discard",\
>> >          }
>> >  
>> >  static QEMUMachine pc_machine_v1_3 = {
>> > 
>> > 
>> 
>> Looks like this was never applied.  Can you redo it for the new 1.5
>> machine (compatibility defines are now in hw/pc.h)?
>> 
>> Paolo
>
> Anthony mentioned that this
>
> http://article.gmane.org/gmane.comp.emulators.qemu/160699
>
> Is the proper way to do it.

That breaks too.  I don't have a solution but I also don't remember what
the exact failures are.

I'm planning on running this patch through testing again so I can
provide better feedback.

Regards,

Anthony Liguori