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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Dec 09, 2015 at 09:32:49AM -0500, Boris Ostrovsky wrote:
> 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@xxxxxxxxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Tested-by: Sander Eikelenboom <linux@xxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

You may want to also add a note saying:

[stable-tree maintainers. Please double-check that you also have
29fa6825463c97e5157284db80107d1bfac5d77b x86, kvm: Clear paravirt_enabled on 
KVM guests for espfix32's benefit
which sets pv_info.paravirt_enabled to zero.]

> ---
>  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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> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel

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