linux-kernel - Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the rtc

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Date:	Wed, 09 Dec 2015 16:00:21 +0100
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>, x86@...nel.org,
	tglx@...utronix.de, xen-devel@...ts.xenproject.org,
	mingo@...hat.com, vkuznets@...hat.com,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org, hpa@...or.com
Subject: Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the
 rtc_cmos platform device

On 2015-12-09 15:42, Jan Beulich wrote:
>>>> On 09.12.15 at 15:32, <boris.ostrovsky@...cle.com> wrote:
>> --- 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;
> 
> What about Xen Dom0?
> 
> Jan

Checked that in my testing and that still worked:
[   16.733837] rtc_cmos 00:02: RTC can wake from S4
[   16.734030] rtc_cmos 00:02: rtc core: registered rtc_cmos as rtc0
[   16.734087] rtc_cmos 00:02: alarms up to one month, y3k, 114 bytes 
nvram
[   17.760329] rtc_cmos 00:02: setting system clock to 2015-12-09 
08:43:48 UTC (1449650628)

and /dev/rtc and /dev/rtc0 both exist.

But i don't know the nitty gritty details about why ...
--
Sander
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