Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753206AbeAQN1B (ORCPT + 1 other); Wed, 17 Jan 2018 08:27:01 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33792 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752888AbeAQN07 (ORCPT ); Wed, 17 Jan 2018 08:26:59 -0500 Date: Wed, 17 Jan 2018 14:25:49 +0100 From: Heiko Carstens To: Martin Schwidefsky Cc: Christian Borntraeger , Florian Weimer , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Cornelia Huck , Greg Kroah-Hartman , Jon Masters , Marcus Meissner , Jiri Kosina Subject: Re: [PATCH 4/6] s390: add system call to run tasks with modified branch prediction References: <1516182519-10623-1-git-send-email-schwidefsky@de.ibm.com> <1516182519-10623-5-git-send-email-schwidefsky@de.ibm.com> <5bda76be-0fec-8165-20bf-5cd8e51e955a@redhat.com> <20180117125506.26f3813c@mschwideX1> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180117125506.26f3813c@mschwideX1> X-TM-AS-GCONF: 00 x-cbid: 18011713-0040-0000-0000-00000425CD8F X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18011713-0041-0000-0000-000020C93EA2 Message-Id: <20180117132549.GC5708@osiris> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-01-17_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1801170193 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Wed, Jan 17, 2018 at 12:55:06PM +0100, Martin Schwidefsky wrote: > On Wed, 17 Jan 2018 12:14:52 +0100 > Christian Borntraeger wrote: > > > On 01/17/2018 11:03 AM, Florian Weimer wrote: > > > On 01/17/2018 10:48 AM, Martin Schwidefsky wrote: > > >> ???????? rc = syscall(__NR_s390_modify_bp); > > >> ???????? if (rc) { > > >> ???????????????? perror("s390_modify_bp"); > > >> ???????????????? exit(EXIT_FAILURE); > > >> ???????? } > > > > > > Isn't this traditionally done through personality or prctl? > > > > I think we want this per thread (and not per process). So I assume personality > > will not work out. Can a prctl be done per thread? > > The prctl interface seems to be usable to set a per-thread control > as well. But there is no architecture specific prctl as far as I > can see. Maybe a common PR_SET_NOBP with an arch function like > arch_set_nobp. There is for example PR_MPX_ENABLE_MANAGEMENT, which is x86 specific. On the other hand x86 even has an arch_prctl() system call... ;)