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 66E02C10F13 for ; Thu, 11 Apr 2019 18:25:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4297F2173C for ; Thu, 11 Apr 2019 18:25:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726630AbfDKSZL (ORCPT ); Thu, 11 Apr 2019 14:25:11 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:59560 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726585AbfDKSZL (ORCPT ); Thu, 11 Apr 2019 14:25:11 -0400 Received: from pps.filterd (m0098410.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x3BIN5GL031916 for ; Thu, 11 Apr 2019 14:25:10 -0400 Received: from e06smtp05.uk.ibm.com (e06smtp05.uk.ibm.com [195.75.94.101]) by mx0a-001b2d01.pphosted.com with ESMTP id 2rt8t7ew99-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 11 Apr 2019 14:25:09 -0400 Received: from localhost by e06smtp05.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) Thu, 11 Apr 2019 19:25:04 +0100 Received: from d06av24.portsmouth.uk.ibm.com (d06av24.portsmouth.uk.ibm.com [9.149.105.60]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x3BIP2AB42663976 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Apr 2019 18:25:02 GMT Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8C0F042049; Thu, 11 Apr 2019 18:25:02 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EB4C44204B; Thu, 11 Apr 2019 18:25:01 +0000 (GMT) Received: from sig-9-145-160-107.de.ibm.com (unknown [9.145.160.107]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Thu, 11 Apr 2019 18:25:01 +0000 (GMT) Date: Thu, 11 Apr 2019 20:25:01 +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: <20190404231622.52531-5-pasic@linux.ibm.com> References: <20190404231622.52531-1-pasic@linux.ibm.com> <20190404231622.52531-5-pasic@linux.ibm.com> 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: 19041118-0020-0000-0000-0000032ED95A X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19041118-0021-0000-0000-000021810B5E Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-11_11:,, 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=1011 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=830 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904110122 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 5 Apr 2019, Halil Pasic wrote: > To support protected virtualization cio will need to make sure the > memory used for communication with the hypervisor is DMA memory. > > Let us introduce a DMA pool to cio that will help us in allocating > deallocating those chunks of memory. > > We use a gen_pool backed with DMA pages to avoid each allocation > effectively wasting a page, as we typically allocate much less > than PAGE_SIZE. 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. Sebastian