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

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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.


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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