From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758235AbdEMT7j (ORCPT ); Sat, 13 May 2017 15:59:39 -0400 Received: from ppsw-30.csi.cam.ac.uk ([131.111.8.130]:51688 "EHLO ppsw-30.csi.cam.ac.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756333AbdEMT7i (ORCPT ); Sat, 13 May 2017 15:59:38 -0400 X-Greylist: delayed 1255 seconds by postgrey-1.27 at vger.kernel.org; Sat, 13 May 2017 15:59:38 EDT X-Cam-AntiVirus: no malware found X-Cam-ScannerInfo: http://help.uis.cam.ac.uk/email-scanner-virus Subject: Re: [Xen-devel] HPET enabled in BIOS, not presented as available_clocksource -- config, kernel code, &/or BIOS? To: pgnet.dev@gmail.com, Randy Dunlap , "linux-kernel@vger.kernel.org" , Clemens Ladisch , xen-devel@lists.xenproject.org References: <61d510e2-0353-ddf2-f63c-8a1688a6b6ed@gmail.com> <9ff8ca5a-727d-13c3-7c39-6383e00d2edf@infradead.org> <2c84903a-ab24-a073-378b-82fe6052e6ac@infradead.org> <927a6245-ae8b-ff4b-d668-a819b8351152@citrix.com> <34c505d9-9dc6-8982-4875-74dedfc5e0d1@gmail.com> From: Andrew Cooper Message-ID: Date: Sat, 13 May 2017 20:59:37 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0 MIME-Version: 1.0 In-Reply-To: <34c505d9-9dc6-8982-4875-74dedfc5e0d1@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/05/2017 20:49, PGNet Dev wrote: > On 5/13/17 12:38 PM, Andrew Cooper wrote: >> What is the issue here? >> >> Xen owns (and may use) any HPETs in the system. They are purposefully >> unavailable to even dom0. > The issue is that, when booting to Xen, hpet is not advertised as an available clocksource, AND reports the hpet boot error pointed out by Randy. > > Following > > https://wiki.xen.org/wiki/Xen_power_management#HPET_as_broadcast_timer_source_.28clocksource.29_.3D > > there's discussion there re: 'if HPET is available / not missing'. > > It appears to be available only booting to non-Xen. > > What specific indication does one look for that Xen's using available hpet? > Ok. Lack of a clocksource is to be expected. The reason why the HPETs are unavailable is that dom0 is not a position to program them; dom0 doesn't know what Xen has set up in the IDT. Use `xl dmesg` to get to the hypervisor dmesg log. You should see mention of the HPET in there if Xen has found it. ~Andrew