On Sun, May 26, 2019 at 08:14:43PM +0200, Jasper Lievisse Adriaanse wrote:
> Hi,
>
> Whilst looking at the mc146818 code in vmd I noticed something that initially
> struck
> me as a pasto as the same code is present in the rtc_update_regb() function.
> However
> it led me to look at how other emulators handle the updating of registers.
> Based on
> that here's a diff to only reschedule the periodic interrupt after updating
> register A
> if something changed in register A.
>
> When updating register A we were checking in register B if the
> PIE bit was set in order to decide if rtc_reschedule_per needed
> to be called. if that bit was changed then the timer rate would
> already have been adjusted by rtc_update_regb so the call from
> rtc_update_rega is not needed. This now matches what qemu and
> other emulators are doing too.
>
> This has been running fine for a few days in a number of VMs.
>
> OK?
>
sure, ok mlarkin
> Index: mc146818.c
> ===
> RCS file: /cvs/src/usr.sbin/vmd/mc146818.c,v
> retrieving revision 1.18
> diff -u -p -r1.18 mc146818.c
> --- mc146818.c12 Jul 2018 10:15:44 - 1.18
> +++ mc146818.c26 May 2019 12:13:32 -
> @@ -216,7 +216,7 @@ rtc_update_rega(uint32_t data)
> __func__);
>
> rtc.regs[MC_REGA] = data;
> - if (rtc.regs[MC_REGB] & MC_REGB_PIE)
> + if ((rtc.regs[MC_REGA] ^ data) & 0x0f)
> rtc_reschedule_per();
> }
>
>
> --
> jasper
>
