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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BC03C433F5 for ; Wed, 6 Oct 2021 13:22:20 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B6CB061075 for ; Wed, 6 Oct 2021 13:22:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org B6CB061075 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 804824076B; Wed, 6 Oct 2021 13:22:19 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 5HmMN8izecYl; Wed, 6 Oct 2021 13:22:18 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id 45545405C3; Wed, 6 Oct 2021 13:22:18 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 19380C0011; Wed, 6 Oct 2021 13:22:18 +0000 (UTC) Received: from smtp1.osuosl.org (smtp1.osuosl.org [140.211.166.138]) by lists.linuxfoundation.org (Postfix) with ESMTP id B59E0C000D for ; Wed, 6 Oct 2021 13:22:16 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id A465483F34 for ; Wed, 6 Oct 2021 13:22:16 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Authentication-Results: smtp1.osuosl.org (amavisd-new); dkim=pass (2048-bit key) header.d=ibm.com Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LzLfJpUkvAeR for ; Wed, 6 Oct 2021 13:22:15 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) by smtp1.osuosl.org (Postfix) with ESMTPS id E20F983F28 for ; Wed, 6 Oct 2021 13:22:15 +0000 (UTC) Received: from pps.filterd (m0098393.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 196D1WeM018298; Wed, 6 Oct 2021 09:21:49 -0400 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=13K13eloHf8ndYtTcY5N4LUEpYMwEaYFKKgqxw1mQsQ=; b=M0jP2wJ2GS/YMXPZddX8eyMVYg8J5bJYUqNzyfTwrOBpnCWiVb9S5tiQlV7s1WoI3gFB yE+uMp75OAm89A8BYdfE9sXKzdftyxua16rjPPx27g3KrVwg/fvgJf3lYSdeUYiH0QcS baaqu+Feo0LdibdJiotzU3TmTibEKwUY58RWI3c25WgeZKx06OI/glaS550wXeFzHiG6 orYE+bJrX9mXN6X/vgCcpqFK06XTFyvu5VUj3L55MKJTwb8VRktxu/7R3K2h2BnRgWcv W54uzmRh5vExP27HHpvWEFLUWNvl3WsZ4IeBfabiYDkSRBb+2dxTtoXwnWOMlR44oy8C Vw== 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 3bhcatrm3p-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 06 Oct 2021 09:21:49 -0400 Received: from pps.filterd (ppma04ams.nl.ibm.com [127.0.0.1]) by ppma04ams.nl.ibm.com (8.16.1.2/8.16.1.2) with SMTP id 196DIj73009373; Wed, 6 Oct 2021 13:21:47 GMT Received: from b06cxnps4076.portsmouth.uk.ibm.com (d06relay13.portsmouth.uk.ibm.com [9.149.109.198]) by ppma04ams.nl.ibm.com with ESMTP id 3bef2b5s0x-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 06 Oct 2021 13:21:46 +0000 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 196DLgpQ62980448 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 6 Oct 2021 13:21:42 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 434454C052; Wed, 6 Oct 2021 13:21:42 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 8F8D84C04A; Wed, 6 Oct 2021 13:21:40 +0000 (GMT) Received: from thinkpad (unknown [9.171.8.189]) by d06av22.portsmouth.uk.ibm.com (Postfix) with SMTP; Wed, 6 Oct 2021 13:21:40 +0000 (GMT) Date: Wed, 6 Oct 2021 15:21:38 +0200 From: Gerald Schaefer To: Hamza Mahfooz , Christoph Hellwig , Dan Williams Subject: Re: DPAA2 triggers, [PATCH] dma debug: report -EEXIST errors in add_dma_entry Message-ID: <20211006152138.160d64e5@thinkpad> In-Reply-To: <20211006151043.61fe9613@thinkpad> References: <20210518125443.34148-1-someguy@effective-light.com> <20210914154504.z6vqxuh3byqwgfzx@skbuf> <185e7ee4-3749-4ccb-6d2e-da6bc8f30c04@linux.ibm.com> <20211001145256.0323957a@thinkpad> <20211006151043.61fe9613@thinkpad> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: jIdONCLNC4SJSBp-4glmMy_Rxf_99vb7 X-Proofpoint-GUID: jIdONCLNC4SJSBp-4glmMy_Rxf_99vb7 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-10-06_02,2021-10-06_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 bulkscore=0 suspectscore=0 phishscore=0 lowpriorityscore=0 mlxlogscore=999 priorityscore=1501 clxscore=1015 mlxscore=0 spamscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2110060082 Cc: linux-s390 , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Jeremy Linton , "iommu@lists.linux-foundation.org" , Ioana Ciornei , Robin Murphy , Karsten Graul X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Wed, 6 Oct 2021 15:10:43 +0200 Gerald Schaefer wrote: > On Fri, 1 Oct 2021 14:52:56 +0200 > Gerald Schaefer wrote: > > > On Thu, 30 Sep 2021 15:37:33 +0200 > > Karsten Graul wrote: > > > > > On 14/09/2021 17:45, Ioana Ciornei wrote: > > > > On Wed, Sep 08, 2021 at 10:33:26PM -0500, Jeremy Linton wrote: > > > >> +DPAA2, netdev maintainers > > > >> Hi, > > > >> > > > >> On 5/18/21 7:54 AM, Hamza Mahfooz wrote: > > > >>> Since, overlapping mappings are not supported by the DMA API we should > > > >>> report an error if active_cacheline_insert returns -EEXIST. > > > >> > > > >> It seems this patch found a victim. I was trying to run iperf3 on a > > > >> honeycomb (5.14.0, fedora 35) and the console is blasting this error message > > > >> at 100% cpu. So, I changed it to a WARN_ONCE() to get the call trace, which > > > >> is attached below. > > > >> > > > > > > > > These frags are allocated by the stack, transformed into a scatterlist > > > > by skb_to_sgvec and then DMA mapped with dma_map_sg. It was not the > > > > dpaa2-eth's decision to use two fragments from the same page (that will > > > > also end un in the same cacheline) in two different in-flight skbs. > > > > > > > > Is this behavior normal? > > > > > > > > > > We see the same problem here and it started with 5.15-rc2 in our nightly CI runs. > > > The CI has panic_on_warn enabled so we see the panic every day now. > > > > Adding a WARN for a case that be detected false-positive seems not > > acceptable, exactly for this reason (kernel panic on unaffected > > systems). > > > > So I guess it boils down to the question if the behavior that Ioana > > described is legit behavior, on a system that is dma coherent. We > > are apparently hitting the same scenario, although it could not yet be > > reproduced with debug printks for some reason. > > > > If the answer is yes, than please remove at lease the WARN, so that > > it will not make systems crash that behave valid, and have > > panic_on_warn set. Even a normal printk feels wrong to me in that > > case, it really sounds rather like you want to fix / better refine > > the overlap check, if you want to report anything here. > > Dan, Christoph, any opinion? > > So far it all looks a lot like a false positive, so could you please > see that those patches get reverted? I do wonder a bit why this is > not an issue for others, we surely cannot be the only ones running > CI with panic_on_warn. For reference, we are talking about these commits: 2b4bbc6231d7 ("dma-debug: report -EEXIST errors in add_dma_entry") 510e1a724ab1 ("dma-debug: prevent an error message from causing runtime problems") The latter introduced the WARN (through err_printk usage), and should be reverted if it can be false-positive, but both seem wrong in that case. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu