Re: [Qemu-devel] [RFC PATCH v8 12/21] replay: recording and replaying different timers

["Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>]

> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> On 22/01/2015 09:52, Pavel Dovgalyuk wrote:
> > This patch introduces functions for recording and replaying realtime sources,
> > that do not use qemu-clock interface. These include return value of time()
> > function in time_t and struct tm forms. Patch also adds warning to
> > get_timedate function to prevent its usage in recording mode, because it may
> > lead to non-determinism.
> >
> > Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
> > ---
> >  hw/timer/mc146818rtc.c   |    3 +
> >  hw/timer/pl031.c         |    3 +
> >  include/qemu-common.h    |    1
> >  replay/replay-internal.h |    4 +
> >  replay/replay-time.c     |  132 ++++++++++++++++++++++++++++++++++++++++++++++
> >  replay/replay.h          |    8 +++
> >  vl.c                     |   17 +++++-
> >  7 files changed, 163 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
> > index f18d128..92295fb 100644
> > --- a/hw/timer/mc146818rtc.c
> > +++ b/hw/timer/mc146818rtc.c
> > @@ -28,6 +28,7 @@
> >  #include "qapi/visitor.h"
> >  #include "qapi-event.h"
> >  #include "qmp-commands.h"
> > +#include "replay/replay.h"
> >
> >  #ifdef TARGET_I386
> >  #include "hw/i386/apic.h"
> > @@ -703,7 +704,7 @@ static void rtc_set_date_from_host(ISADevice *dev)
> >      RTCState *s = MC146818_RTC(dev);
> >      struct tm tm;
> >
> > -    qemu_get_timedate(&tm, 0);
> 
> What about just making qemu_get_timedate use
> qemu_clock_get_ns(QEMU_CLOCK_HOST) instead of time()?  This would just
> work using the infrastructure of the previous patch.

I can get rid of these calls, but localtime() function used
in qemu_get_timedate() will not work deterministically. 
Should we save its' result then?

Pavel Dovgalyuk