From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753344AbbHUHqa (ORCPT ); Fri, 21 Aug 2015 03:46:30 -0400 Received: from terminus.zytor.com ([198.137.202.10]:47455 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751585AbbHUHq2 (ORCPT ); Fri, 21 Aug 2015 03:46:28 -0400 Date: Fri, 21 Aug 2015 00:45:50 -0700 From: tip-bot for Vitaly Kuznetsov Message-ID: Cc: hpa@zytor.com, vkuznets@redhat.com, peterz@infradead.org, tglx@linutronix.de, haiyangz@microsoft.com, mingo@kernel.org, linux-kernel@vger.kernel.org, kys@microsoft.com, torvalds@linux-foundation.org Reply-To: mingo@kernel.org, haiyangz@microsoft.com, tglx@linutronix.de, peterz@infradead.org, hpa@zytor.com, vkuznets@redhat.com, kys@microsoft.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org In-Reply-To: <1440003264-9949-1-git-send-email-vkuznets@redhat.com> References: <1440003264-9949-1-git-send-email-vkuznets@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/platform] x86/hyperv: Mark the Hyper-V TSC as unstable Git-Commit-ID: 88c9281a9fba67636ab26c1fd6afbc78a632374f X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 88c9281a9fba67636ab26c1fd6afbc78a632374f Gitweb: http://git.kernel.org/tip/88c9281a9fba67636ab26c1fd6afbc78a632374f Author: Vitaly Kuznetsov AuthorDate: Wed, 19 Aug 2015 09:54:24 -0700 Committer: Ingo Molnar CommitDate: Fri, 21 Aug 2015 08:44:38 +0200 x86/hyperv: Mark the Hyper-V TSC as unstable The Hyper-V top-level functional specification states, that "algorithms should be resilient to sudden jumps forward or backward in the TSC value", this means that we should consider TSC as unstable. In some cases tsc tests are able to detect the instability, it was detected in 543 out of 646 boots in my testing: Measured 6277 cycles TSC warp between CPUs, turning off TSC clock. tsc: Marking TSC unstable due to check_tsc_sync_source failed This is, however, just a heuristic. On Hyper-V platform there are two good clocksources: MSR-based hyperv_clocksource and recently introduced TSC page. Signed-off-by: Vitaly Kuznetsov Cc: Haiyang Zhang Cc: K. Y. Srinivasan Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: devel@linuxdriverproject.org Link: http://lkml.kernel.org/r/1440003264-9949-1-git-send-email-vkuznets@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/mshyperv.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index aad4bd8..6fd023d 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -141,6 +141,7 @@ static void __init ms_hyperv_init_platform(void) no_timer_check = 1; #endif + mark_tsc_unstable("running on Hyper-V"); } const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {