[Xen-devel] Re: [Qemu-devel] [PATCH 1/4] xen: introduce mc146818rtcxen

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 15 Nov 2011, Stefano Stabellini wrote:
> On Tue, 15 Nov 2011, Anthony Liguori wrote:
> > On 11/15/2011 08:51 AM, stefano.stabellini@xxxxxxxxxxxxx wrote:
> > > From: Stefano Stabellini<stefano.stabellini@xxxxxxxxxxxxx>
> > >
> > > Xen doesn't need full RTC emulation in Qemu because the RTC is already
> > > emulated by the hypervisor. In particular we want to avoid the timers
> > > initialization so that Qemu doesn't need to wake up needlessly.
> > >
> > > Signed-off-by: Stefano Stabellini<stefano.stabellini@xxxxxxxxxxxxx>
> > 
> > Yuck.  There's got to be a better way to do this.
> 
> Yeah, it is pretty ugly, I was hoping in some good suggestions to
> improve this patch :)
> 
> 
> > I think it would be better to name timers and then in Xen specific machine 
> > code, 
> > disable the RTC timers.
> 
> Good idea!
> I was thinking that I could implement an rtc_stop function in
> mc146818rtc.c that stops and frees the timers.
> 
> Now the problem is that from xen-all.c I cannot easily find the
> ISADevice instance to pass to rtc_stop. Do you think it would be
> reasonable to call rtc_stop from pc_basic_device_init, inside the same
> if (!xen_available()) introduce by the next patch?
> 
> Otherwise I could implement functions to walk the isa bus, similarly to
> pci_for_each_device.
> 

ping?


> This is just an example:
> 
> diff --git a/hw/mc146818rtc.c b/hw/mc146818rtc.c
> index 2aaca2f..568c540 100644
> --- a/hw/mc146818rtc.c
> +++ b/hw/mc146818rtc.c
> @@ -667,6 +667,28 @@ ISADevice *rtc_init(int base_year, qemu_irq 
> intercept_irq)
>      return dev;
>  }
>  
> +void rtc_stop(ISADevice *dev)
> +{
> +    RTCState *s = DO_UPCAST(RTCState, dev, dev);
> +
> +    qemu_del_timer(s->periodic_timer);
> +    qemu_del_timer(s->second_timer);
> +    qemu_del_timer(s->second_timer2);
> +#ifdef TARGET_I386
> +    if (rtc_td_hack) {
> +        qemu_del_timer(s->coalesced_timer);
> +    }
> +#endif
> +    qemu_free_timer(s->periodic_timer);
> +    qemu_free_timer(s->second_timer);
> +    qemu_free_timer(s->second_timer2);
> +#ifdef TARGET_I386
> +    if (rtc_td_hack) {
> +        qemu_free_timer(s->coalesced_timer);
> +    }
> +#endif
> +}
> +
>  static ISADeviceInfo mc146818rtc_info = {
>      .qdev.name     = "mc146818rtc",
>      .qdev.size     = sizeof(RTCState),
> diff --git a/hw/mc146818rtc.h b/hw/mc146818rtc.h
> index 575968c..aa2b8ab 100644
> --- a/hw/mc146818rtc.h
> +++ b/hw/mc146818rtc.h
> @@ -8,5 +8,6 @@
>  ISADevice *rtc_init(int base_year, qemu_irq intercept_irq);
>  void rtc_set_memory(ISADevice *dev, int addr, int val);
>  void rtc_set_date(ISADevice *dev, const struct tm *tm);
> +void rtc_stop(ISADevice *dev);
>  
>  #endif /* !MC146818RTC_H */
> diff --git a/hw/pc.c b/hw/pc.c
> index a0ae981..d734f75 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -1145,6 +1145,8 @@ void pc_basic_device_init(qemu_irq *gsi,
>  
>      if (!xen_available()) {
>          pit = pit_init(0x40, 0);
> +    } else {
> +        rtc_stop(*rtc_state);
>      }
>      pcspk_init(pit);
>  
> 

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