From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH,UNPARSEABLE_RELAY,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BF84AC43A1D for ; Thu, 12 Jul 2018 00:06:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E0702146E for ; Thu, 12 Jul 2018 00:06:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="LjpyNvh2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7E0702146E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403802AbeGLANN (ORCPT ); Wed, 11 Jul 2018 20:13:13 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:35446 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390950AbeGLANJ (ORCPT ); Wed, 11 Jul 2018 20:13:09 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w6C04GM9185734; Thu, 12 Jul 2018 00:04:35 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : subject : date : message-id : in-reply-to : references; s=corp-2018-07-02; bh=xf8NcDpJwtO/V0QLuZ8RwMQDwm40h+cLXIf+6TAB+oY=; b=LjpyNvh2BzYWVN364Mf8K0tPOWAlXaiTuFg+K1rowyN49dF6ZHpxafpZOEsSLlxQflm0 0vXWpNrNHEF9i23DfeAjbIWn0zuxUM6Fc77oNTNUltHW2JSwZbrwyXqKItq6ISh5oqCu /wYhNf/T0Sf5jidwCkZi0VC8NvSeOXLnYXWzPDopnwC/yKWo3Hi8HNACrZhfiMoBGcgM Uc/aYtX+5amQ0hxLsVXDesUasraG8VoZ/KC+Bq2vbb6zTlNL/IGXsN/YFvK/Ec3ezZOu NVwXqh4hFj7p2PFEYKzifT0I/9D3RlWpNnSPkv2iw30S1Mf/dxW0XrEu5/uS3UYWDnGx Qw== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by aserp2120.oracle.com with ESMTP id 2k2p7e09ge-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 12 Jul 2018 00:04:35 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w6C04YYa012979 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 12 Jul 2018 00:04:34 GMT Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w6C04WcC004553; Thu, 12 Jul 2018 00:04:32 GMT Received: from localhost.localdomain (/73.69.118.222) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 11 Jul 2018 17:04:32 -0700 From: Pavel Tatashin To: steven.sistare@oracle.com, daniel.m.jordan@oracle.com, linux@armlinux.org.uk, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, john.stultz@linaro.org, sboyd@codeaurora.org, x86@kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com, douly.fnst@cn.fujitsu.com, peterz@infradead.org, prarit@redhat.com, feng.tang@intel.com, pmladek@suse.com, gnomes@lxorguk.ukuu.org.uk, linux-s390@vger.kernel.org, pasha.tatashin@oracle.com, boris.ostrovsky@oracle.com, jgross@suse.com Subject: [PATCH v13 04/18] x86/tsc: redefine notsc to behave as tsc=unstable Date: Wed, 11 Jul 2018 20:04:05 -0400 Message-Id: <20180712000419.5165-5-pasha.tatashin@oracle.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20180712000419.5165-1-pasha.tatashin@oracle.com> References: <20180712000419.5165-1-pasha.tatashin@oracle.com> X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8951 signatures=668706 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807110252 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently, notsc kernel parameter disables the use of tsc register by sched_clock(). However, this parameter does not prevent linux from accessing tsc in other places in kernel. The only rational to boot with notsc is to avoid timing discrepancies on multi-socket systems where different tsc frequencies may present, and thus fallback to jiffies for clock source. However, there is another method to solve the above problem, it is to boot with tsc=unstable parameter. This parameter allows sched_clock() to use tsc but in case tsc is outside of expected interval it is corrected back to a sane value. This is why there is no reason to keep notsc, and it can be removed. But, for compatibility reasons we will keep this parameter but change its definition to be the same as tsc=unstable. Signed-off-by: Pavel Tatashin Reviewed-by: Dou Liyang Reviewed-by: Thomas Gleixner --- .../admin-guide/kernel-parameters.txt | 2 -- Documentation/x86/x86_64/boot-options.txt | 4 +--- arch/x86/kernel/tsc.c | 18 +++--------------- 3 files changed, 4 insertions(+), 20 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index efc7aa7a0670..f7123d28f318 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2835,8 +2835,6 @@ nosync [HW,M68K] Disables sync negotiation for all devices. - notsc [BUGS=X86-32] Disable Time Stamp Counter - nowatchdog [KNL] Disable both lockup detectors, i.e. soft-lockup and NMI watchdog (hard-lockup). diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt index 8d109ef67ab6..66114ab4f9fe 100644 --- a/Documentation/x86/x86_64/boot-options.txt +++ b/Documentation/x86/x86_64/boot-options.txt @@ -92,9 +92,7 @@ APICs Timing notsc - Don't use the CPU time stamp counter to read the wall time. - This can be used to work around timing problems on multiprocessor systems - with not properly synchronized CPUs. + Deprecated, use tsc=unstable instead. nohpet Don't use the HPET timer. diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 74392d9d51e0..186395041725 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -38,11 +38,6 @@ EXPORT_SYMBOL(tsc_khz); */ static int __read_mostly tsc_unstable; -/* native_sched_clock() is called before tsc_init(), so - we must start with the TSC soft disabled to prevent - erroneous rdtsc usage on !boot_cpu_has(X86_FEATURE_TSC) processors */ -static int __read_mostly tsc_disabled = -1; - static DEFINE_STATIC_KEY_FALSE(__use_tsc); int tsc_clocksource_reliable; @@ -248,8 +243,7 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable); #ifdef CONFIG_X86_TSC int __init notsc_setup(char *str) { - pr_warn("Kernel compiled with CONFIG_X86_TSC, cannot disable TSC completely\n"); - tsc_disabled = 1; + mark_tsc_unstable("boot parameter notsc"); return 1; } #else @@ -1307,7 +1301,7 @@ static void tsc_refine_calibration_work(struct work_struct *work) static int __init init_tsc_clocksource(void) { - if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz) + if (!boot_cpu_has(X86_FEATURE_TSC) || !tsc_khz) return 0; if (tsc_unstable) @@ -1414,12 +1408,6 @@ void __init tsc_init(void) set_cyc2ns_scale(tsc_khz, cpu, cyc); } - if (tsc_disabled > 0) - return; - - /* now allow native_sched_clock() to use rdtsc */ - - tsc_disabled = 0; static_branch_enable(&__use_tsc); if (!no_sched_irq_time) @@ -1455,7 +1443,7 @@ unsigned long calibrate_delay_is_known(void) int constant_tsc = cpu_has(&cpu_data(cpu), X86_FEATURE_CONSTANT_TSC); const struct cpumask *mask = topology_core_cpumask(cpu); - if (tsc_disabled || !constant_tsc || !mask) + if (!constant_tsc || !mask) return 0; sibling = cpumask_any_but(mask, cpu); -- 2.18.0