From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760101Ab3B0BVm (ORCPT ); Tue, 26 Feb 2013 20:21:42 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:41728 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759879Ab3BZX5E (ORCPT ); Tue, 26 Feb 2013 18:57:04 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Olaf Hering , "K. Y. Srinivasan" , "H. Peter Anvin" Subject: [ 010/150] x86: Hyper-V: register clocksource only if its advertised Date: Tue, 26 Feb 2013 15:54:27 -0800 Message-Id: <20130226235525.185835105@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130226235523.930663721@linuxfoundation.org> References: <20130226235523.930663721@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Olaf Hering <[mailto:olaf@aepfle.de]> commit 32068f6527b8f1822a30671dedaf59c567325026 upstream. Enable hyperv_clocksource only if its advertised as a feature. XenServer 6 returns the signature which is checked in ms_hyperv_platform(), but it does not offer all features. Currently the clocksource is enabled unconditionally in ms_hyperv_init_platform(), and the result is a hanging guest. Hyper-V spec Bit 1 indicates the availability of Partition Reference Counter. Register the clocksource only if this bit is set. The guest in question prints this in dmesg: [ 0.000000] Hypervisor detected: Microsoft HyperV [ 0.000000] HyperV: features 0x70, hints 0x0 This bug can be reproduced easily be setting 'viridian=1' in a HVM domU .cfg file. A workaround without this patch is to boot the HVM guest with 'clocksource=jiffies'. Signed-off-by: Olaf Hering Link: http://lkml.kernel.org/r/1359940959-32168-1-git-send-email-kys@microsoft.com Signed-off-by: K. Y. Srinivasan Signed-off-by: H. Peter Anvin Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/cpu/mshyperv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -68,7 +68,8 @@ static void __init ms_hyperv_init_platfo printk(KERN_INFO "HyperV: features 0x%x, hints 0x%x\n", ms_hyperv.features, ms_hyperv.hints); - clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100); + if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE) + clocksource_register_hz(&hyperv_cs, NSEC_PER_SEC/100); } const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {