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=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_2 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 41E3DC71155 for ; Mon, 30 Nov 2020 08:56:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B71692076E for ; Mon, 30 Nov 2020 08:56:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=ibm.com header.i=@ibm.com header.b="HzBBi3dm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727857AbgK3I4i (ORCPT ); Mon, 30 Nov 2020 03:56:38 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:27046 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726270AbgK3I4i (ORCPT ); Mon, 30 Nov 2020 03:56:38 -0500 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 0AU8WjhT159060; Mon, 30 Nov 2020 03:55:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ibm.com; h=date : from : to : cc : subject : message-id : in-reply-to : references : mime-version : content-type : content-transfer-encoding; s=pp1; bh=g2vNIH73GKpHarEpLnkjsrzo54bJhlCVWTzhmiy3Xq4=; b=HzBBi3dmrhtHDXsYIj9EZpXfUYdEM5aqYprzFZoD0QvYSQkKWahsbIgMX4c5MGVrr8WV POC333oPZ5m18oVqnXm3bobY/xAgXjDkQfumBbgHGh4layJ56mSLCd6JBEuEJK8W+VAn +USwsyznL4lLsNt0tuL0RP21kPb0BEjWa/abU/d1p6p68XLAOKraZm5+6hK3BX88GXCM 0YICqwFWfaBHJ17w29fbeRfbzagMTjW6aCLZMA/wy8vFEmd4YQHKcp8iR5lveE35hls6 h2ZpmqZG3tMJaxQ0CUK+iwaZejZ5YcC1zFfLsJEYhZ1a1hLej3aegY8+bV9XYOgwwKyG 4A== Received: from ppma04ams.nl.ibm.com (63.31.33a9.ip4.static.sl-reverse.com [169.51.49.99]) by mx0a-001b2d01.pphosted.com with ESMTP id 354w7v0pfp-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 30 Nov 2020 03:55:56 -0500 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.0.42/8.16.0.42) with SMTP id 0AU8loZT007949; Mon, 30 Nov 2020 08:55:54 GMT Received: from b06cxnps4075.portsmouth.uk.ibm.com (d06relay12.portsmouth.uk.ibm.com [9.149.109.197]) by ppma04ams.nl.ibm.com with ESMTP id 353e681u2w-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 30 Nov 2020 08:55:54 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0AU8tpg16292148 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 30 Nov 2020 08:55:51 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B8E104C04E; Mon, 30 Nov 2020 08:55:51 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6D7C44C046; Mon, 30 Nov 2020 08:55:51 +0000 (GMT) Received: from oc2783563651 (unknown [9.171.74.188]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 30 Nov 2020 08:55:51 +0000 (GMT) Date: Mon, 30 Nov 2020 09:55:49 +0100 From: Halil Pasic To: Niklas Schnelle Cc: Alexander Gordeev , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] s390/pci: fix CPU address in MSI for directed IRQ Message-ID: <20201130095549.27da927f.pasic@linux.ibm.com> In-Reply-To: <2400bc6a-ff0a-f0b8-66fc-25e11032dacb@linux.ibm.com> References: <1606410037-11436-1-git-send-email-agordeev@linux.ibm.com> <20201127095633.60f8a544.pasic@linux.ibm.com> <16fe9017-407f-1bb0-1599-fb46d93009fc@linux.ibm.com> <20201127163936.38a51c15.pasic@linux.ibm.com> <2400bc6a-ff0a-f0b8-66fc-25e11032dacb@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-30_02:2020-11-30,2020-11-30 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 mlxscore=0 mlxlogscore=999 clxscore=1015 adultscore=0 phishscore=0 malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011300055 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 30 Nov 2020 09:30:33 +0100 Niklas Schnelle wrote: > I'm not really familiar, with it but I think this is closely related > to what I asked Bernd Nerz. I fear that if CPUs go away we might already > be in trouble at the firmware/hardware/platform level because the CPU Add= ress is > "programmed into the device" so to speak. Thus a directed interrupt from > a device may race with anything reordering/removing CPUs even if > CPU addresses of dead CPUs are not reused and the mapping is stable. =46rom your answer, I read that CPU hot-unplug is supported for LPAR.=20 >=20 > Furthermore our floating fallback path will try to send a SIGP > to the target CPU which clearly doesn't work when that is permanently > gone. Either way I think these issues are out of scope for this fix > so I will go ahead and merge this. I agree, it makes on sense to delay this fix. But if CPU hot-unplug is supported, I believe we should react when a CPU is unplugged, that is a target of directed interrupts. My guess is, that in this scenario transient hiccups are unavoidable, and thus should be accepted, but we should make sure that we recover. Regards, Halil