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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE autolearn=no 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 81719C433ED for ; Fri, 7 May 2021 20:04:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5646261436 for ; Fri, 7 May 2021 20:04:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230103AbhEGUF6 (ORCPT ); Fri, 7 May 2021 16:05:58 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:21366 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230096AbhEGUF5 (ORCPT ); Fri, 7 May 2021 16:05:57 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.43/8.16.0.43) with SMTP id 147K2nEa080669; Fri, 7 May 2021 16:04:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=mime-version : content-transfer-encoding : content-type : date : message-id : subject : from : to : cc : references : in-reply-to; s=pp1; bh=TQQlpVtOKlN8C1Bt7HJaAi2NsujWr/1T15UMuWjKOG4=; b=GpC5RFZku+uvKwCq4qbxquezmvoFjPeRyOt/kaEcyty0VmhBIAWore2SA9aLiZzcJGwp PJcNuJQb4VqhlI/G4wEh8DMQVREhibJBC2GS4vQnquCNWlKLOp4A66aQrUY8mIHgtjVx SOc3gm9yaaBE0rRydnVjXh1NJsZm0bf7rH1+UJ+HrHVB/ZYmhk+1STBS35nPyNm4Q6Zc X/6+3DPYV+fetn+pJ/frtAAwJSumJ3kRp7wtdwsJ8kDJaGO/A2KRhyOOu0gxudD4X3x3 EJqhsch8JyGSEiiL2J3R+pIlX2xvKVnHKdZPfcDajd4czcp2VNtht6VDzZWgAoDikARY Yw== Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0a-001b2d01.pphosted.com with ESMTP id 38d84bffyu-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 May 2021 16:04:05 -0400 Received: from pps.filterd (ppma02dal.us.ibm.com [127.0.0.1]) by ppma02dal.us.ibm.com (8.16.0.43/8.16.0.43) with SMTP id 147K43qD014539; Fri, 7 May 2021 20:04:05 GMT Received: from b03cxnp07028.gho.boulder.ibm.com (b03cxnp07028.gho.boulder.ibm.com [9.17.130.15]) by ppma02dal.us.ibm.com with ESMTP id 38csqnftg4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Fri, 07 May 2021 20:04:05 +0000 Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp07028.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 147K3s2Y22282536 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 7 May 2021 20:03:54 GMT Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 35118BE059; Fri, 7 May 2021 20:03:54 +0000 (GMT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7E359BE04F; Fri, 7 May 2021 20:03:53 +0000 (GMT) Received: from oc8246131445.ibm.com (unknown [9.160.141.26]) by b03ledav005.gho.boulder.ibm.com (Postfix) with SMTP; Fri, 7 May 2021 20:03:53 +0000 (GMT) Received: from localhost (localhost6 [IPv6:::1]) by oc8246131445.ibm.com (Postfix) with ESMTP id 220D6BC0D7B; Fri, 7 May 2021 15:03:51 -0500 (CDT) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Fri, 07 May 2021 15:03:51 -0500 Message-Id: Subject: Re: [RESEND PATCH v4 10/11] powerpc: Protect patching_mm with a lock From: "Christopher M. Riedl" To: "Peter Zijlstra" Cc: , , , , References: <20210506043452.9674-1-cmr@linux.ibm.com> <20210506043452.9674-11-cmr@linux.ibm.com> In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: IAfPKIgqzEtDXpl3GCYp0ZEkSYkOkS3q X-Proofpoint-ORIG-GUID: IAfPKIgqzEtDXpl3GCYp0ZEkSYkOkS3q X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-05-07_08:2021-05-06,2021-05-07 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 mlxscore=0 priorityscore=1501 spamscore=0 impostorscore=0 malwarescore=0 suspectscore=0 lowpriorityscore=0 clxscore=1011 mlxlogscore=643 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2105070131 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Thu May 6, 2021 at 5:51 AM CDT, Peter Zijlstra wrote: > On Wed, May 05, 2021 at 11:34:51PM -0500, Christopher M. Riedl wrote: > > Powerpc allows for multiple CPUs to patch concurrently. When patching > > with STRICT_KERNEL_RWX a single patching_mm is allocated for use by all > > CPUs for the few times that patching occurs. Use a spinlock to protect > > the patching_mm from concurrent use. > >=20 > > Modify patch_instruction() to acquire the lock, perform the patch op, > > and then release the lock. > >=20 > > Also introduce {lock,unlock}_patching() along with > > patch_instruction_unlocked() to avoid per-iteration lock overhead when > > patch_instruction() is called in a loop. A follow-up patch converts som= e > > uses of patch_instruction() to use patch_instruction_unlocked() instead= . > > x86 uses text_mutex for all this, why not do the same? I wasn't entirely sure if there is a problem with potentially going to sleep in some of the places where patch_instruction() is called - the spinlock avoids that (hypothetical) problem. I just tried switching to text_mutex and at least on a P9 machine the series boots w/ the Hash and Radix MMUs (with some lockdep errors). I can rework this in the next version to use text_mutex if I don't find any new problems with more extensive testing. It does mean more changes to use patch_instruction_unlocked() in kprobe/optprobe/ftace in arch/powerpc since iirc those are called with text_mutex already held. Thanks! Chris R.