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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 27EAAC10F14 for ; Tue, 15 Oct 2019 19:43:50 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 7B1C920663 for ; Tue, 15 Oct 2019 19:43:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B1C920663 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=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46t5TH1VYvzDr4D for ; Wed, 16 Oct 2019 06:43:47 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=linux.ibm.com (client-ip=148.163.156.1; helo=mx0a-001b2d01.pphosted.com; envelope-from=fbarrat@linux.ibm.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.ibm.com Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46t5R86GKHzDqyg for ; Wed, 16 Oct 2019 06:41:55 +1100 (AEDT) Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x9FJb9b6133178 for ; Tue, 15 Oct 2019 15:41:51 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2vnkx793fw-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Tue, 15 Oct 2019 15:41:51 -0400 Received: from localhost by e06smtp07.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, 15 Oct 2019 20:41:46 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x9FJfjCi40305116 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 15 Oct 2019 19:41:45 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 40DD5AE045; Tue, 15 Oct 2019 19:41:45 +0000 (GMT) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 131A4AE053; Tue, 15 Oct 2019 19:41:45 +0000 (GMT) Received: from pic2.home (unknown [9.145.66.182]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 15 Oct 2019 19:41:45 +0000 (GMT) Subject: Re: [EXTERNAL] [RFC PATCH] powernv/eeh: Fix oops when probing cxl devices To: Sam Bobroff References: <20190927124510.15518-1-fbarrat@linux.ibm.com> <20191015054219.GA16918@osmium> From: Frederic Barrat Date: Tue, 15 Oct 2019 21:41:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191015054219.GA16918@osmium> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19101519-0028-0000-0000-000003AA55B8 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19101519-0029-0000-0000-0000246C6CB9 Message-Id: <8bf2ff79-e3a1-89cd-98af-dfddf9056d01@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-10-15_06:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 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=8.0.1-1908290000 definitions=main-1910150167 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: clombard@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, andrew.donnellan@au1.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 15/10/2019 à 07:42, Sam Bobroff a écrit : > On Fri, Sep 27, 2019 at 02:45:10PM +0200, Frederic Barrat wrote: >> Recent cleanup in the way EEH support is added to a device causes a >> kernel oops when the cxl driver probes a device and creates virtual >> devices discovered on the FPGA: >> >> BUG: Kernel NULL pointer dereference at 0x000000a0 >> Faulting instruction address: 0xc000000000048070 >> Oops: Kernel access of bad area, sig: 7 [#1] >> ... >> NIP [c000000000048070] eeh_add_device_late.part.9+0x50/0x1e0 >> LR [c00000000004805c] eeh_add_device_late.part.9+0x3c/0x1e0 >> Call Trace: >> [c000200e43983900] [c00000000079e250] _dev_info+0x5c/0x6c (unreliable) >> [c000200e43983980] [c0000000000d1ad0] pnv_pcibios_bus_add_device+0x60/0xb0 >> [c000200e439839f0] [c0000000000606d0] pcibios_bus_add_device+0x40/0x60 >> [c000200e43983a10] [c0000000006aa3a0] pci_bus_add_device+0x30/0x100 >> [c000200e43983a80] [c0000000006aa4d4] pci_bus_add_devices+0x64/0xd0 >> [c000200e43983ac0] [c00800001c429118] cxl_pci_vphb_add+0xe0/0x130 [cxl] >> [c000200e43983b00] [c00800001c4242ac] cxl_probe+0x504/0x5b0 [cxl] >> [c000200e43983bb0] [c0000000006bba1c] local_pci_probe+0x6c/0x110 >> [c000200e43983c30] [c000000000159278] work_for_cpu_fn+0x38/0x60 >> >> The root cause is that those cxl virtual devices don't have a >> representation in the device tree and therefore no associated pci_dn >> structure. In eeh_add_device_late(), pdn is NULL, so edev is NULL and >> we oops. >> >> We never had explicit support for EEH for those virtual >> devices. Instead, EEH events are reported to the (real) pci device and >> handled by the cxl driver. Which can then forward to the virtual >> devices and handle dependencies. The fact that we try adding EEH >> support for the virtual devices is new and a side-effect of the recent >> cleanup. >> >> This patch fixes it by skipping adding EEH support on powernv for >> devices which don't have a pci_dn structure. >> >> Fixes: b905f8cdca77 ("powerpc/eeh: EEH for pSeries hot plug") >> Signed-off-by: Frederic Barrat >> --- >> >> Sending as an RFC, as I'm afraid of hiding potential issues and would >> be interested in comments. The powernv eeh code expects a struct >> pci_dn, so the fix seems safe. I'm wondering if there could be cases >> (other than capi virtual devices) where we'd want to blow up and fix >> instead of going undetected with this patch. > > Looks good to me. > > I do think it would be good to detect a missing pci_dn (WARN_ONCE() > might be appropriate). However to implement it, > pnv_pcibios_bus_add_device() would need a way to detect that a struct > pci_dev is a cxl virtual device. I don't see an easy way to do that; do > you know if it's possible? I think I found a solution. There's a cxl_pci_is_vphb_device() which is fairly cheap and would do the job. Sorry, I didn't think about it at first. > One last thing: pseries_pcibios_bus_add_device() also requires a pci_dn. > Do you know if it's possible to trigger a similar issue there, or is it > not possible for some reason? I don't think anybody is using capi in a lpar, but it should theorically be possible to hit it. I'll dig some more tomorrow and adjust the patch when resubmitting. Thanks! Fred > > Cheers, > Sam. > >> arch/powerpc/platforms/powernv/eeh-powernv.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/powerpc/platforms/powernv/eeh-powernv.c b/arch/powerpc/platforms/powernv/eeh-powernv.c >> index 6bc24a47e9ef..6f300ab7f0e9 100644 >> --- a/arch/powerpc/platforms/powernv/eeh-powernv.c >> +++ b/arch/powerpc/platforms/powernv/eeh-powernv.c >> @@ -42,7 +42,7 @@ void pnv_pcibios_bus_add_device(struct pci_dev *pdev) >> { >> struct pci_dn *pdn = pci_get_pdn(pdev); >> >> - if (eeh_has_flag(EEH_FORCE_DISABLED)) >> + if (!pdn || eeh_has_flag(EEH_FORCE_DISABLED)) >> return; >> >> dev_dbg(&pdev->dev, "EEH: Setting up device\n"); >> -- >> 2.21.0 >>