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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham 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 9D89CC10F13 for ; Tue, 16 Apr 2019 12:50:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 769B0205ED for ; Tue, 16 Apr 2019 12:50:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728650AbfDPMuW (ORCPT ); Tue, 16 Apr 2019 08:50:22 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:54876 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727030AbfDPMuW (ORCPT ); Tue, 16 Apr 2019 08:50:22 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3GCj3XD016503 for ; Tue, 16 Apr 2019 08:50:21 -0400 Received: from e06smtp03.uk.ibm.com (e06smtp03.uk.ibm.com [195.75.94.99]) by mx0b-001b2d01.pphosted.com with ESMTP id 2rwe3k3jsx-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 16 Apr 2019 08:50:20 -0400 Received: from localhost by e06smtp03.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 16 Apr 2019 13:50:17 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3GCoF1D51904686 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 16 Apr 2019 12:50:15 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 9B6975205A; Tue, 16 Apr 2019 12:50:15 +0000 (GMT) Received: from dyn-9-152-212-168.boeblingen.de.ibm.com (unknown [9.152.212.168]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTPS id 1EB9F5204E; Tue, 16 Apr 2019 12:50:15 +0000 (GMT) Date: Tue, 16 Apr 2019 14:50:14 +0200 (CEST) From: Sebastian Ott X-X-Sender: sebott@schleppi To: Halil Pasic cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, Cornelia Huck , Martin Schwidefsky , virtualization@lists.linux-foundation.org, Christian Borntraeger , Viktor Mihajlovski , Vasily Gorbik , Janosch Frank , Claudio Imbrenda , Farhan Ali , Eric Farman Subject: Re: [RFC PATCH 04/12] s390/cio: introduce cio DMA pool In-Reply-To: <20190412173017.04b768bb@oc2783563651> References: <20190404231622.52531-1-pasic@linux.ibm.com> <20190404231622.52531-5-pasic@linux.ibm.com> <20190412132010.3c74cb63@oc2783563651> <20190412173017.04b768bb@oc2783563651> User-Agent: Alpine 2.21 (LFD 202 2017-01-01) Organization: =?ISO-8859-15?Q?=22IBM_Deutschland_Research_&_Development_GmbH?= =?ISO-8859-15?Q?_=2F_Vorsitzende_des_Aufsichtsrats=3A_Matthias?= =?ISO-8859-15?Q?_Hartmann_Gesch=E4ftsf=FChrung=3A_Dirk_Wittkopp?= =?ISO-8859-15?Q?_Sitz_der_Gesellschaft=3A_B=F6blingen_=2F_Reg?= =?ISO-8859-15?Q?istergericht=3A_Amtsgericht_Stuttgart=2C_HRB_2432?= =?ISO-8859-15?Q?94=22?= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-TM-AS-GCONF: 00 x-cbid: 19041612-0012-0000-0000-0000030F69C4 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041612-0013-0000-0000-00002147A2E2 Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-16_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904160086 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 12 Apr 2019, Halil Pasic wrote: > On Fri, 12 Apr 2019 14:12:31 +0200 (CEST) > Sebastian Ott wrote: > > On Fri, 12 Apr 2019, Halil Pasic wrote: > > > On Thu, 11 Apr 2019 20:25:01 +0200 (CEST) > > > Sebastian Ott wrote: > > > > I don't think we should use this global DMA pool. I guess it's OK for > > > > stuff like airq (where we don't have a struct device at hand) but for > > > > CCW we should use the device we have. Yes, this way we waste some memory > > > > but all dma memory a device uses should fit in a page - so the wastage > > > > is not too much. > > Regarding the wastage. Let us do the math together in search for an > upper (wastage) limit. [...] > Currently we need at least 224 bytes per device that is ~ 6% > of a PAGE_SIZE. Yes, we basically waste the whole page. I'm ok with that if the benefit is to play nice with the kernel APIs. > > For practical > > matters: DMA debugging will complain about misuse of a specific device or > > driver. > > > > Do you mean CONFIG_DMA_API_DEBUG and CONFIG_DMA_API_DEBUG_SG? I've been > running with those and did not see any complaints. Maybe we should > clarify this one offline... I didn't mean to imply that there are bugs already - just that when used as intended the DMA_DEBUG_API can complain about stuff like "your device is gone but you have still DMA memory set up for it" which will not work if you don't use the correct device... Sebastian