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[PATCH] x86: Xen PV guests don't have the rtc_cmos platform device

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Adding the rtc platform device in a Xen PV guests causes an IRQ
conflict because these guests do not have a legacy PIC.

In a single VCPU Xen PV guest we should have:

/proc/interrupts:
           CPU0
  0:       4934  xen-percpu-virq      timer0
  1:          0  xen-percpu-ipi       spinlock0
  2:          0  xen-percpu-ipi       resched0
  3:          0  xen-percpu-ipi       callfunc0
  4:          0  xen-percpu-virq      debug0
  5:          0  xen-percpu-ipi       callfuncsingle0
  6:          0  xen-percpu-ipi       irqwork0
  7:        321   xen-dyn-event     xenbus
  8:         90   xen-dyn-event     hvc_console
  ...

But hvc_console cannot get its interrupt because it is already in use
by rtc0 and the console does not work.

  genirq: Flags mismatch irq 8. 00000000 (hvc_console) vs. 00000000 (rtc0)

So don't add the rtc_cmos device in Xen PV guests. (In fact, don't add
it to any paravirt_enabled() guest since lguest is also unable to probe
this device)

Reported-by: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: Sander Eikelenboom <linux@eikelenboom.it>
Cc: stable@vger.kernel.org
---
 arch/x86/kernel/rtc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index cd96852..dd4d6d9 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -200,6 +200,9 @@ static __init int add_rtc_cmos(void)
 	}
 #endif
 
+	if (paravirt_enabled())
+		return -ENODEV;
+
 	platform_device_register(&rtc_device);
 	dev_info(&rtc_device.dev,
 		 "registered platform RTC device (no PNP device found)\n");
-- 
1.8.1.4

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[PATCH] x86: Xen PV guests don't have the rtc_cmos platform device Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-09 15:40 +0100
  Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the  rtc_cmos platform device "Jan Beulich" <JBeulich@suse.com> - 2015-12-09 15:50 +0100
    Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the  rtc_cmos platform device Sander Eikelenboom <linux@eikelenboom.it> - 2015-12-09 16:10 +0100
      Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the rtc_cmos  platform device Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-09 16:20 +0100
        Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the  rtc_cmos platform device "Jan Beulich" <JBeulich@suse.com> - 2015-12-09 16:30 +0100
          Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the rtc_cmos  platform device Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-09 19:20 +0100
      Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the rtc_cmos platform device Vitaly Kuznetsov <vkuznets@redhat.com> - 2015-12-09 16:30 +0100

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