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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D57B9C7EE2D for ; Tue, 9 May 2023 06:16:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234821AbjEIGQU (ORCPT ); Tue, 9 May 2023 02:16:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33872 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234820AbjEIGQS (ORCPT ); Tue, 9 May 2023 02:16:18 -0400 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BBE09A5D8; Mon, 8 May 2023 23:16:16 -0700 (PDT) Received: from pps.filterd (m0353727.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 34965apF011425; Tue, 9 May 2023 06:14:10 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=pp1; bh=FINnFngIr9A5li2quYo/MMeJgUXiyZsHissNFC4A/Dc=; b=mQiqKmKYgzRD8Sxg5n+wWapC9P/MT9T8G+xii/b6Gkh30aDaSNhEpSq13VH5vq9ogv+u VTWu6GA6tUkGhnVdBC1iPW0h2ZQTaEpE3YpYJu88OBLZzmyccBdgScj7EJR5iioHlIKj 61+ux+xVxEXgcjGf9WSiSFYvwQYJNv9RFD8ydlXg4I6LNVZiCItX4YEmIqJ5ZlbJDlau XRJX8OUjw0ftnHh1uKybbdkAaXcgeDfne2FUKl15NM5NBBcMKKEPBUcvRvnAGnZuPFcU gsuUMkLSL2tarHc6RLbm+IkeW4GEYCCnzFxjEaao5bvXGqGnHTvlCwab12WX/ODJYaPK DA== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3qfgdv0q5j-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 May 2023 06:14:10 +0000 Received: from m0353727.ppops.net (m0353727.ppops.net [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 34965tFX013528; Tue, 9 May 2023 06:14:09 GMT Received: from ppma04fra.de.ibm.com (6a.4a.5195.ip4.static.sl-reverse.com [149.81.74.106]) by mx0a-001b2d01.pphosted.com (PPS) with ESMTPS id 3qfgdv0q4a-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 May 2023 06:14:08 +0000 Received: from pps.filterd (ppma04fra.de.ibm.com [127.0.0.1]) by ppma04fra.de.ibm.com (8.17.1.19/8.17.1.19) with ESMTP id 3493QkaD023577; Tue, 9 May 2023 06:14:05 GMT Received: from smtprelay02.fra02v.mail.ibm.com ([9.218.2.226]) by ppma04fra.de.ibm.com (PPS) with ESMTPS id 3qf7d1r5nj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 09 May 2023 06:14:05 +0000 Received: from smtpav03.fra02v.mail.ibm.com (smtpav03.fra02v.mail.ibm.com [10.20.54.102]) by smtprelay02.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 3496E20f38207824 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 9 May 2023 06:14:02 GMT Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 107072004F; Tue, 9 May 2023 06:14:02 +0000 (GMT) Received: from smtpav03.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A335620040; Tue, 9 May 2023 06:14:00 +0000 (GMT) Received: from osiris (unknown [9.152.212.90]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 9 May 2023 06:14:00 +0000 (GMT) Date: Tue, 9 May 2023 08:13:59 +0200 From: Heiko Carstens To: Peter Zijlstra Cc: bigeasy@linutronix.de, mark.rutland@arm.com, maz@kernel.org, catalin.marinas@arm.com, will@kernel.org, chenhuacai@kernel.org, kernel@xen0n.name, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, pbonzini@redhat.com, wanpengli@tencent.com, vkuznets@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, jgross@suse.com, boris.ostrovsky@oracle.com, daniel.lezcano@linaro.org, kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, rafael@kernel.org, longman@redhat.com, boqun.feng@gmail.com, pmladek@suse.com, senozhatsky@chromium.org, rostedt@goodmis.org, john.ogness@linutronix.de, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jstultz@google.com, sboyd@kernel.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [RFC][PATCH 6/9] s390/time: Provide sched_clock_noinstr() Message-ID: References: <20230508211951.901961964@infradead.org> <20230508213147.786238095@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230508213147.786238095@infradead.org> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: wfDGl-FeFqMNDJw0P2Xjgk-_X25VGp__ X-Proofpoint-ORIG-GUID: 6h-NLR-B9IcQaofOg1gSserw9vYicRYB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-09_03,2023-05-05_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 clxscore=1011 lowpriorityscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 impostorscore=0 phishscore=0 bulkscore=0 mlxscore=0 mlxlogscore=834 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2304280000 definitions=main-2305090046 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 1;115;0cOn Mon, May 08, 2023 at 11:19:57PM +0200, Peter Zijlstra wrote: > With the intent to provide local_clock_noinstr(), a variant of > local_clock() that's safe to be called from noinstr code (with the > assumption that any such code will already be non-preemptible), > prepare for things by providing a noinstr sched_clock_noinstr() > function. > > Specifically, preempt_enable_*() calls out to schedule(), which upsets > noinstr validation efforts. > > Signed-off-by: Peter Zijlstra (Intel) > --- > arch/s390/include/asm/timex.h | 13 +++++++++---- > arch/s390/kernel/time.c | 11 ++++++++++- > 2 files changed, 19 insertions(+), 5 deletions(-) ... > +static __always_inline unsigned long __get_tod_clock_monotonic(void) > +{ > + return get_tod_clock() - tod_clock_base.tod; > +} > + > /** > * get_clock_monotonic - returns current time in clock rate units > * > @@ -216,7 +221,7 @@ static inline unsigned long get_tod_cloc > unsigned long tod; > > preempt_disable_notrace(); > - tod = get_tod_clock() - tod_clock_base.tod; > + tod = __get_tod_clock_monotonic(); > preempt_enable_notrace(); > return tod; > } ... > +unsigned long long noinstr sched_clock_noinstr(void) > +{ > + return tod_to_ns(__get_tod_clock_monotonic()); > +} > + > /* > * Scheduler clock - returns current time in nanosec units. > */ > unsigned long long notrace sched_clock(void) > { > - return tod_to_ns(get_tod_clock_monotonic()); > + unsigned long long ns; > + preempt_disable_notrace(); > + ns = tod_to_ns(get_tod_clock_monotonic()); > + preempt_enable_notrace(); > + return ns; > } > NOKPROBE_SYMBOL(sched_clock); This disables preemption twice within sched_clock(). So this should either call __get_tod_clock_monotonic() instead, or the function could stay as it is, which I would prefer.