RE: [PATCH v2 1/2] x86: restore pv_rtc_handler() invocation

[Paul Durrant <xadimgnik@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: 15 July 2020 10:47
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>; Paul Durrant <paul@xxxxxxx>; 
> Wei Liu <wl@xxxxxxx>;
> Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Subject: [PATCH v2 1/2] x86: restore pv_rtc_handler() invocation
> 
> This was lost when making the logic accessible to PVH Dom0.
> 
> Fixes: 835d8d69d96a ("x86/rtc: provide mediated access to RTC for PVH dom0")
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/arch/x86/time.c
> +++ b/xen/arch/x86/time.c
> @@ -1160,6 +1160,10 @@ void rtc_guest_write(unsigned int port,
>      case RTC_PORT(1):
>          if ( !ioports_access_permitted(currd, RTC_PORT(0), RTC_PORT(1)) )
>              break;
> +
> +        if ( pv_rtc_handler )
> +            pv_rtc_handler(currd->arch.cmos_idx & 0x7f, data);
> +

This appears to be semantically slightly different to the old code in that it 
is only done for a write to RC_PORT(1), whereas it would have been done on a 
write to either RTC_POR(0) or RTC_PORT(1) before. Is that of any concern?

  Paul

>          spin_lock_irqsave(&rtc_lock, flags);
>          outb(currd->arch.cmos_idx & 0x7f, RTC_PORT(0));
>          outb(data, RTC_PORT(1));