Re: [Qemu-devel] [PATCH 2/2] Change timedrift default value to slew

[Anthony Liguori]

On 03/20/2012 02:48 PM, Crístian Viana wrote:
> Windows 2008+ is very sensitive to missed ticks.  The RTC is used by default as
> the time source.  If time drift is not enabled, Windows is prone to
> blue screening.
>
> Signed-off-by: Crístian Viana<address@hidden>
> ---
>   vl.c |   13 ++++++++++++-
>   1 files changed, 12 insertions(+), 1 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 112b0e0..2c7cbf0 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -550,11 +550,22 @@ static void configure_rtc(QemuOpts *opts)
>
>               qdev_prop_register_global_list(slew_lost_ticks);
>           } else if (!strcmp(value, "none")) {
> -            /* discard is default */
> +            /* do nothing */
>           } else {
>               fprintf(stderr, "qemu: invalid option value '%s'\n", value);
>               exit(1);
>           }
> +    } else {
> +        static GlobalProperty slew_lost_ticks[] = {
> +            {
> +                .driver   = "mc146818rtc",
> +                .property = "lost_tick_policy",
> +                .value    = "slew",
> +            },
> +            { /* end of list */ }
> +        };

I think we just want to change:

hw/mc146818rtc.h:
    DEFINE_PROP_LOSTTICKPOLICY("lost_tick_policy", RTCState,
                               lost_tick_policy, LOST_TICK_DISCARD),

I think we just need to change this to LOST_TICK_SLEW.  This would effectively 
change the default.

Regards,

Anthony Liguori

> +        qdev_prop_register_global_list(slew_lost_ticks);
>       }
>   }