linux-kernel - Re: [Xen-devel] [PATCHv1] x86: rtc_cmos platform device requires legacy irqs

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Date:	Tue, 8 Dec 2015 16:15:43 -0500
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	David Vrabel <david.vrabel@...rix.com>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCHv1] x86: rtc_cmos platform device requires
 legacy irqs

On 12/08/2015 04:02 PM, Thomas Gleixner wrote:
> On Fri, 4 Dec 2015, David Vrabel wrote:
>> On 04/12/15 14:06, David Vrabel wrote:
>>> On 03/12/15 10:43, David Vrabel wrote:
>>>> Adding the rtc platform device when there are no legacy irqs (no
>>>> legacy PIC) causes a conflict with other devices that end up using the
>>>> same irq number.
>>> An alternative is to remove the rtc_cmos platform device in Xen PV
>>> guests.
>>>
>>> Any preference on how this regression should be fixed?
>>>
>>> David
>>>
>>> 8<--------------------------
>>> x86: Xen PV guests don't have the rtc_cmos platform device
>>>
>> [...]
>>> --- 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 (xen_pv_domain())
>>> +		return -ENODEV;
>>> +
>> Note there's a missing include that breaks !XEN builds.
> What's the state of this?

I think we are waiting for x86 maintainers to express their preference. 
There were 3 proposals to add in add_rtc_cmos()

1. if (!nr_legacy_irqs())
             return -ENODEV;

2. #ifdef XEN
         if (xen_pv_domain())
                 return -ENODEV;
     #endif

3. if (paravirt_enabled())
             return -ENODEV;


-boris
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