Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754014AbbLISTT (ORCPT ); Wed, 9 Dec 2015 13:19:19 -0500 Received: from userp1040.oracle.com ([156.151.31.81]:32314 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753470AbbLISTQ (ORCPT ); Wed, 9 Dec 2015 13:19:16 -0500 Subject: Re: [Xen-devel] [PATCH] x86: Xen PV guests don't have the rtc_cmos platform device To: Jan Beulich , Sander Eikelenboom References: <1449671569-4540-1-git-send-email-boris.ostrovsky@oracle.com> <56684BD402000078000BDB00@prv-mh.provo.novell.com> <745827c24ef5e59808d725d5777b5698@eikelenboom.it> <56684595.4040402@oracle.com> <5668566202000078000BDB6E@prv-mh.provo.novell.com> Cc: David Vrabel , x86@kernel.org, tglx@linutronix.de, xen-devel@lists.xenproject.org, mingo@redhat.com, vkuznets@redhat.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, hpa@zytor.com From: Boris Ostrovsky Message-ID: <56687091.6090400@oracle.com> Date: Wed, 9 Dec 2015 13:18:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <5668566202000078000BDB6E@prv-mh.provo.novell.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1744 Lines: 46 On 12/09/2015 10:27 AM, Jan Beulich wrote: >>>> On 09.12.15 at 16:15, wrote: >> On 12/09/2015 10:00 AM, Sander Eikelenboom wrote: >>> On 2015-12-09 15:42, Jan Beulich wrote: >>>>>>> On 09.12.15 at 15:32, 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 ... >> >> That's because it is discovered by ACPI earlier. I don't know though >> whether we can always assume this will be the case. > I don't think we should - Dom0 should (device-wise) behave just > like a native kernel. So maybe then this is the case for having a feature flag (probably in pv_info) that marks which features are paravirtualized. Vitaly suggested it earlier but I thought we won't have use for it until we get to HVMlite with variable set of fetures. -boris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/