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 7A380C433F5 for ; Mon, 13 Dec 2021 15:21:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237614AbhLMPV6 (ORCPT ); Mon, 13 Dec 2021 10:21:58 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:31114 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234691AbhLMPV5 (ORCPT ); Mon, 13 Dec 2021 10:21:57 -0500 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 1BDEvTRu019387; Mon, 13 Dec 2021 15:21:56 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=6uKATVOKq+6mYEI33gn8wVbbiuB1hYGRL4/Y7PgKOvg=; b=BbbXXECVBIVUv2Hs/xY3cnyp7v6wXqtXt6imc96KcLBLyikiVsG2q/gub1n0rIJCYfIO +Tu+YnAW6E/fmkoaxWzJHoGOcDBTUr0KNARiwI9+yWKNAd7uxBe8z1aHLZoW5y2gYQW3 s95i+GWVuEOXxUR7SlJ6W1te6SB0rrcB+IqSSLarJBqfXdooVTDeIeaq/PFGDnZBVNWO k03rTtGB27p4Z+Z83ArFK6XmqpoHJz2zxxfp95MXQImccKxKUpo6YLOYXh8OJvbbT8p4 +K1nHYsKlto0fmGe8GcFrUb/4PamKNIMXEQ2zHZi2a/sXUUbTFp5jiAKntKZVuCYjMCJ 2g== Received: from pps.reinject (localhost [127.0.0.1]) by mx0a-001b2d01.pphosted.com with ESMTP id 3cx8d5rn9r-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Dec 2021 15:21:56 +0000 Received: from m0098417.ppops.net (m0098417.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.43/8.16.0.43) with SMTP id 1BDEw6Yi021488; Mon, 13 Dec 2021 15:21:55 GMT Received: from ppma01fra.de.ibm.com (46.49.7a9f.ip4.static.sl-reverse.com [159.122.73.70]) by mx0a-001b2d01.pphosted.com with ESMTP id 3cx8d5rn93-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Dec 2021 15:21:55 +0000 Received: from pps.filterd (ppma01fra.de.ibm.com [127.0.0.1]) by ppma01fra.de.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 1BDFGObU019407; Mon, 13 Dec 2021 15:21:54 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma01fra.de.ibm.com with ESMTP id 3cvkm95gf7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 13 Dec 2021 15:21:54 +0000 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 1BDFLoPk45875530 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 13 Dec 2021 15:21:50 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7928711C054; Mon, 13 Dec 2021 15:21:50 +0000 (GMT) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0923C11C058; Mon, 13 Dec 2021 15:21:50 +0000 (GMT) Received: from osiris (unknown [9.145.30.170]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Mon, 13 Dec 2021 15:21:49 +0000 (GMT) Date: Mon, 13 Dec 2021 16:21:48 +0100 From: Heiko Carstens To: Pierre Morel Cc: Claudio Imbrenda , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, cohuck@redhat.com, david@redhat.com, thuth@redhat.com, gor@linux.ibm.com Subject: Re: [PATCH v5 1/1] s390x: KVM: accept STSI for CPU topology information Message-ID: References: <20211122131443.66632-1-pmorel@linux.ibm.com> <20211122131443.66632-2-pmorel@linux.ibm.com> <20211209133616.650491fd@p-imbrenda> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-TM-AS-GCONF: 00 X-Proofpoint-GUID: rbZSwQ6fN-gLUW7L53MWdD_SF9YAAjh6 X-Proofpoint-ORIG-GUID: 34Tv4CDkq_d8m36HdaOhT7gYESxjxibC X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2021-12-13_06,2021-12-13_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 priorityscore=1501 mlxlogscore=677 spamscore=0 suspectscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 bulkscore=0 adultscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2112130097 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 13, 2021 at 03:26:58PM +0100, Pierre Morel wrote: > > Why is this assumption necessary? The statement that Linux runs only > > with horizontal polarization is not true. > > > > Right, I will rephrase this as: > > "Polarization change is not taken into account, QEMU intercepts queries for > polarization change (PTF) and only provides horizontal polarization > indication to Guest's Linux." > > @Heiko, I did not find any usage of the polarization in the kernel other > than an indication in the sysfs. Is there currently other use of the > polarization that I did not see? You can change polarization by writing to /sys/devices/system/cpu/dispatching. Or alternativel use the chcpu tool to change polarization. There is however no real support for vertical polarization implemented in the kernel. Therefore changing to vertical polarization is _not_ recommended, since it will most likely have negative performance impacts on your Linux system. However the interface is still there for experimental purposes.