From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.kundenserver.de (mout.kundenserver.de [217.72.192.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B2A0A35A95D; Mon, 19 Jan 2026 12:53:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.72.192.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768827193; cv=none; b=tC/HyW7kgA0Mx/W/9ZxSfJStznI66ZtyZGIv1yU3CFKZbDq2Jps/uWW51qLcww6izDYp9SI03XfUnwAPBqa/lOWTY19XfUnJox/UwRUAgohGBbkbSjl4gMaxNAGcXr9u+EeE6102oF/76wFQjcA02Y7exBPpqqKquGWk1t2tJlQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768827193; c=relaxed/simple; bh=cGzPxUmaEhFMDDElzlC+0Cv5UBY7+PeNviT+AavSgPM=; h=Message-ID:Date:MIME-Version:To:Cc:References:From:Subject: In-Reply-To:Content-Type; b=XBy6lM7v3xJ0xJpMYMM6NT+KDEG/F1FpeD4+fdrhVa5dfM23+kr1PTCAWxp3PAlgZLnwM/cy9JH5Gak4z8+nxfsUK+7q19696Do4/8X7fBxmYdGzS9Tk/FhtRvarN5bRUqvOjee9bEh6AaZ7U9OlAouFB7VF7Lmp9xCJ91V6TlQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=green-communications.fr; spf=pass smtp.mailfrom=green-communications.fr; arc=none smtp.client-ip=217.72.192.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=green-communications.fr Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=green-communications.fr Received: from [192.168.0.66] ([88.171.60.104]) by mrelayeu.kundenserver.de (mreue106 [213.165.67.119]) with ESMTPSA (Nemesis) id 1M3lLh-1vhXll1nPv-00BvaZ; Mon, 19 Jan 2026 13:53:02 +0100 Message-ID: <154d0ccb-00d8-4e7b-ab6e-c798c86c5e96@green-communications.fr> Date: Mon, 19 Jan 2026 13:53:01 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Robin Murphy , iommu@lists.linux.dev, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Bjorn Helgaas , "Rob Herring (Arm)" , Lorenzo Pieralisi , Jason Gunthorpe , regressions@lists.linux.dev References: <3780eb61-68e2-42ce-939e-7458cd3a63cb@green-communications.fr> <4da29d46-9a80-4ec4-b6b8-6c9457eed481@arm.com> Content-Language: en-US From: Nicolas Cavallari Autocrypt: addr=Nicolas.Cavallari@green-communications.fr; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:qvKrgniDhCDttoq4hx/KpwZ7wvT16Hg+QjDEhqguqFoZvTWbYYU TAdm6qt5OYVkrkzIV5BNU900bXM0nA2ibuHysJmVsMFcS3Dg0a4BXevHAaml5stE7+brjh3 G4BzfnZqu694rkvzCdqJNoOeJi8QMlhuL9ygtzBVxeOTgA/J20A8OqLub9ESDr49En8OwaK +/xqqWg7onaVG+Ll/CRpQ== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:EzNrFn9xkI4=;8DWpBIhuMNpzgSwAxfQ7dLLhNe9 rJznxzuVIOeaoZU+8zdc6bMAZaWOX191m6YuvJF5zlTkEmbgVD76qPgO2Y1+coVr+LuwZ7JnS vWk0I9WuOlH+m1ytpblAoqYRY96llCe8Pzci9ZO5u1kt1mBzaXWEMUW+eHPPHvvm4cSRd/JXv ah4YpGGGRpYevF3UGKuYeVBPCSL1qwF0iA4n3tRK+B9nx2MHdGv06+qTWpErTQCTYvQy7yok4 gdkp/Ee6x25tSvq77PZnH2qECgCo1ZJK7lkeJgCwmtlREFQ0Bnhu8jnkseS6K2SXEinx1v2hf SmZRjmJZQ058ec6scJu2PqT2n3HQq77r41V4DfU+krCzqwEVajaS8roagNgmgcDA1MrzI/bG2 UQBgtjxbXPlRYbTf+s4QCcPDfXBSn9NN2gQZLM5L6Uq00VcdMD7ddzpLKIenPuWkA7gIJ6K/x agvLGJ8nCORN15CgDuHgfbh/y2il346tDwqB5nvxV/R1SfZX4JUBBGLCpkmrhYY9rGdNLYAQG roa/daAv/oxjZ4Tvek6wb/Mz7MwDrjQG93OxqqtaTdKGjnTK5ySOEVf+igyeCP9fpfA+AK7oa sSYgMYB0tYEGZVwMXI+NqxaamqdrtpyjpWHHDYF1wfZ/H6qWkIDmYqmIAMeeYZMsmjFeODxtz VGJmFV9wwn75kCh+EbzZ3Fz19QtoKTBD8ozTOUfoYVJkXdwYV9rbTdRTCg4EImIUH4c/KDrhT S7wllpqjgmIWJMkRlIKRwhwMghd8Us8Cyibhid1SnTJwVxh8RGhy/xzqhCpqObd+1TALqC4t/ RvHHBbe2TMKQvDM5YKb7idT9v9u4NxABJnzrj2ergxqCnhy+QqsE6yXaEiKA56jbJ+oC7dkcz IESEsG8o1x/twrNAYL1vWJ92u/xPAlfjPn6nb3zFeT2U7ohRnZ6ggzFl6ckw+1mX8lDJXgl2Y F4xyRlSgc6Obeo3vXuF7K+lIfkiWOXILcOQIBec7VzgRmdLKxJ73BdNuG0FMpQ7oD+8Nq3krC +1hR2NDLjxYnvTotm0+fW9PPWIud2zy5I7DT8YImSXU1wK2vFBfj6x9WZXb/2PshORP4fECPi WodrPNUNlqFRPVKI6F50ZHUHZUqJpZpNyBKOG+BEKybe6TH9x/nMy3YSl/HvLf0lb2CqHb8tY KunLjb+t/RYsMZTzWCxqTwKbqyb9L4mm+S3sPyztpRu3Y5wkBOnO8AGJkA1WsSFZcAVwIcWZG JkVlZW3t5a3LBU6y0p8aSU0V723JuuewIFxWJ+nfdsOU2yeKlyIg4PVeeWgzmez+OVMI9k81I dymPt+Cbi4LKFwE2rNpcP/m39WetK5OxfAjAb42vnG6ZGZlVmdm7Z/4sHpXBtXyThpm99aTzX Ett3mzhWu6Wf3B61dj08mRdMuNJWlC9VxeGO1cIOChKqEGGKkhGiaAzUaaIgDakSURwIURcFF ePlfCCSyvVNrywAEcPG8i9zJ7glah4NRtSXEswqJqfieME0kgE4k2qhwRXI+4wnWlWjfqDVPq XRbp+KH4wfyRdQCXXJeh7i11vrZWRNfa8a3E+gH0Xj/jRe9D8d80h5OXHpzKXGUuPPPQoZI/a njzlisWadfTYQDLM6Z4xZhCXxsouGvGNld9dXQji/2C1NWCpSLmAnXP1vj2E9rGGoJ41GXA/8 o0d+fXB7Lzn7lioyi0zaeWREgrmHOHgWsxvOc7WkP+8yrij30gT8zTp8TZp5B6SSVBTbnVLTR 3A+45Nf6RjQgu1oaPsoP/Dd9+Ao7WG9EY07XFd4J9JRPvzEsXsUgCqQqy7X5jiodVkYqg1mqB Sjcp Le 16/01/2026 à 18:24, Robin Murphy a écrit : > On 2026-01-16 4:52 pm, Nicolas Cavallari wrote: >> +cc regressions ML >> >> Le 13/01/2026 à 10:17, Nicolas Cavallari a écrit : >>> +cc patch author & reviewers >>> >>> On 1/9/26 17:22, Nicolas Cavallari wrote: >>>> When upgrading from 6.12 to a 6.18 kernel, I noticed that a PCI >>>> Ethernet adapter (Microchip LAN7430) would hang under load and not >>>> recover.  When that happens, some of its registers indicate it is >>>> failing to do DMA reads, so cannot reclaim entries on its ring buffer. >>>> >>>> I bisected the problem into this commit: >>>> >>>> commit bcb81ac6ae3c2ef95b44e7b54c3c9522364a245c >>>> Author: Robin Murphy >>>> Date:   Fri Feb 28 15:46:33 2025 +0000 >>>> >>>>       iommu: Get DT/ACPI parsing into the proper probe path >>>> >>>> The problem still exists on 6.19-rc1, on pci/next (29a77b4897f1) and on >>>> iommu/master (360e85353769) trees.  Reverting the commit fixes the >>>> issue. >> >> The problem persists on 6.19-rc5 >> >>>> The system is a Gateworks GW7200, which is a i.MX 8 Mini connected to a >>>> Pericom >>>> PI7C9X2G404 4-port switch connected to the LAN7430 chip. >>>> >>>> -[0000:00]---00.0-[01-ff]----00.0-[02-05]--+-01.0-[03]----00.0 >>>>                                              +-02.0-[04]-- >>>>                                              \-03.0-[05]----00.0 >>>> >>>> The problem only occurs when there is at least another PCI device in use >>>> on the >>>> switch.  It does not happen if the LAN7430 is the only PCI device, or if >>>> the >>>> other devices are not actively used.  For example i can reproduce it >>>> with an >>>> ath9k wireless network adapter when it is up and running, but not when >>>> it is >>>> down or its driver is not loaded. >>>> >>>> I suspect that other PCI devices have similar issues, but the LAN7430 is >>>> the >>>> easiest one to diagnose, as it hangs within seconds with an iperf3 -- >>>> bidir -u >>>> -b 200M and its register map are public. >>>> >>>> I couldn't find an way to dump the PCI address translation mapping from >>>> userspace. >>>> I would be happy to provide more information or test patches. >> >> I debugged it further, it seems to be mostly a PCI issue since the >> system does not actually have an IOMMU. > > Indeed, I was figuring this had to be another case of a switch with > wonky ACS - do Mani's patches adjusting ACS enablement make any difference? > > https://lore.kernel.org/all/20260102-pci_acs-v3-1-72280b94d288@oss.qualcomm.com/ With this series, ACS is still enabled and eth1 is still failing under load. > Although in this case I guess the issue is arguably more that we're > requesting ACS at all, before we know that there's actually an IOMMU > present to warrant it. Clearly the best option would be to figure out if > the switch behaviour itself can be fixed somehow, but perhaps something > like this might help paper over the issue for now (but I'd have to test > it to make sure it doesn't break IOMMUs again...) > > ----->8----- > diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c > index 6b989a62def2..837cc0b5ace4 100644 > --- a/drivers/iommu/of_iommu.c > +++ b/drivers/iommu/of_iommu.c > @@ -141,10 +141,12 @@ int of_iommu_configure(struct device *dev, struct > device_node *master_np, > .np = master_np, > }; > > - pci_request_acs(); > err = pci_for_each_dma_alias(to_pci_dev(dev), > of_pci_iommu_init, &info); > - of_pci_check_device_ats(dev, master_np); > + if (!err) { > + pci_request_acs(); > + of_pci_check_device_ats(dev, master_np); > + } > } else { > err = of_iommu_configure_device(master_np, dev, id); > } > -----8<----- With this, ACS is indeed disabled and eth1 no longer fails under load, but I have also identified an errata on the PCIe switch that causes ACS to fail. 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