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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 71AEEC32793 for ; Wed, 18 Jan 2023 19:28:19 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pIE5r-0005CZ-0S; Wed, 18 Jan 2023 14:27:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pIE5o-0005CP-EH for qemu-devel@nongnu.org; Wed, 18 Jan 2023 14:27:28 -0500 Received: from mail-sn1nam02on20629.outbound.protection.outlook.com ([2a01:111:f400:7ea9::629] helo=NAM02-SN1-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pIE5m-0005Z8-8H for qemu-devel@nongnu.org; Wed, 18 Jan 2023 14:27:28 -0500 ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=AAyQqU4kHLhtNHByFNaJC5/YWbAL1Z8si2bySuD6GWtPvDnbwvJOb1mS5TKyO8jNnUlYKxHJj+3KsPOyasP7HQ7qr22HCjKUf41uOtgWxPcW8csii47ZxLJ4GzR1M4+6Ej9qgj041jub9mf2FXWicTmsGpGUG4DHYChfiKgfqnu9PouwDKkVo4VYOpS0tVkHqiEk4XZt2+LNK/PMQV1GmlFVPkOKm1AHP+GCOMfK7Z6VrvoeAwO4/Srqg/CCW/3cBBtwSPyRtyCif6YZbKtYEOPmnsBA4om1rrf15tz6LEYZDg21+sXxmMWAa65gPFVfh79OqBAZWVGk8RpsBnR4xQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=vWbogzutPyancKoCF6PKTmYO5jZdv45t/4wlNyI7PME=; b=Mh3CYs80LhjG7rtkeiaof2L1f3fxIj4Mi/YhH9J5r6PaPTfFt0mBsQ1UosxKt/naVpTx5JAEiii7tNFoM8PyGNdy9j2gSLLWLzMONlg8/HYa5aEAj1jrRLzYiGr/9Rwtdw/hMdDxVBHanf8VYGRF9O+C4ItiGLpRmEpJN5+NFWh+k8X7y0kGi2HjNuXgaSOpd9HwygMbMBbsakaU5RKUIJHeYr8tUz/zxaJ+mFI+BWRPkKxz9YH6cZO6lyqEdmgtojUWmJx1BiNTlue0fYapzuH/yVxHUw6tXZga58E6tWvakZ9t7eoYjo3CRFpdh9ocu8P+DkiMJPRM3lR2V561hQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=memverge.com; dmarc=pass action=none header.from=memverge.com; dkim=pass header.d=memverge.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=memverge.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=vWbogzutPyancKoCF6PKTmYO5jZdv45t/4wlNyI7PME=; b=qjnzaRW2v/+CVfFAawHy8fNGlyVZMFqgT4fJeivs7Ll8+OA9g9rgqylTfDNENEwufBCZAxlDqMhLauZQT8uar5kcv0iuqLVfi/TelYWLIclKEkby88RmgFtlZ/AVOriBAlMM2/dvqecIbjuiIeWnERjK4GABnzn1moZNV7gKwAY= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=memverge.com; Received: from BN6PR17MB3121.namprd17.prod.outlook.com (2603:10b6:405:7c::19) by BY5PR17MB3762.namprd17.prod.outlook.com (2603:10b6:a03:239::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5986.23; Wed, 18 Jan 2023 19:22:20 +0000 Received: from BN6PR17MB3121.namprd17.prod.outlook.com ([fe80::d253:1eb3:9347:c660]) by BN6PR17MB3121.namprd17.prod.outlook.com ([fe80::d253:1eb3:9347:c660%4]) with mapi id 15.20.5986.023; Wed, 18 Jan 2023 19:22:19 +0000 Date: Wed, 18 Jan 2023 14:22:08 -0500 From: Gregory Price To: Lukas Wunner Cc: Jonathan Cameron , qemu-devel@nongnu.org, Michael Tsirkin , Ben Widawsky , linux-cxl@vger.kernel.org, linuxarm@huawei.com, Ira Weiny , Gregory Price Subject: Re: [PATCH 0/8] hw/cxl: CXL emulation cleanups and minor fixes for upstream Message-ID: References: <20230111142440.24771-1-Jonathan.Cameron@huawei.com> <20230112172130.0000391b@Huawei.com> <20230113091213.00002146@Huawei.com> <20230113144026.000001fb@Huawei.com> <20230113144511.00001207@Huawei.com> <20230113151206.GA20583@wunner.de> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230113151206.GA20583@wunner.de> X-ClientProxiedBy: BY5PR04CA0013.namprd04.prod.outlook.com (2603:10b6:a03:1d0::23) To BN6PR17MB3121.namprd17.prod.outlook.com (2603:10b6:405:7c::19) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN6PR17MB3121:EE_|BY5PR17MB3762:EE_ X-MS-Office365-Filtering-Correlation-Id: faf0ff5f-1d56-4bd4-e993-08daf9895131 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255; CTRY:; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:BN6PR17MB3121.namprd17.prod.outlook.com; PTR:; CAT:NONE; SFS:(13230022)(39830400003)(136003)(396003)(376002)(366004)(346002)(451199015)(2616005)(66946007)(66476007)(186003)(8676002)(26005)(6916009)(6512007)(4326008)(66556008)(41300700001)(36756003)(86362001)(5660300002)(8936002)(38100700002)(478600001)(54906003)(83380400001)(316002)(6506007)(6666004)(2906002)(45080400002)(6486002)(4001150100001)(44832011); DIR:OUT; SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?soLJHl0WTVd8DI4h+5L/kSkJNXkKXEnZgnqPB2aLouB66V5cheQkg3UQ36AB?= =?us-ascii?Q?ioeACnFIKXvf4bFqXNoD6X+eCQnRUorYfU8U0ol/audGSMozahz6pebX9KlE?= =?us-ascii?Q?a18Cr2JfwtLJH+F8vsyPq5QiRO2p7uosLCZXuWLdsIrxg1SLxlZNYndLcZSS?= =?us-ascii?Q?ZEI5RVtG+puMR4wsI/9VZw9YF8VIQQDNxzalzT3mePkGzqBxuTHDjjIDZHbY?= =?us-ascii?Q?+VWPKtSFE6ZjpUAPzIm32A0bFEz947RJ7Qs9y3E+NAlvgF78yBByBERf3/Qd?= =?us-ascii?Q?TLJnR1Lu6bbGjq3otVk9HQfe/52ykBcAXDS7Xc1FyrfaXa5MOS3tloo1YrQ3?= =?us-ascii?Q?9c1l0iAgQmFaj4n5RKO7gjh80QeTAJBlzk2afwhr3BhVJ+EfkPK+67hDvw8i?= =?us-ascii?Q?op8DKbCHAt/Vlfw2Ag8wkxFF6QBU7vUUkn6XI4hwEAotk2RxpMoZkNSIs5Yp?= =?us-ascii?Q?cjCxViquGX1ppV41Pxv9inImL7e0wwPUzw/Kw2P4t2RtO8YEF04RTnzhagMT?= =?us-ascii?Q?56EbV2bgAsLVgVL01frRksBWCM/AZHzA1RHE/x3tjKcQWjpizOba6H3cUqsG?= =?us-ascii?Q?OzvzEIwXHy2dXTCkkD+dLdl5nFVPU9vLvcI0ITts3NQIg0YqqRVQVtVwim4D?= =?us-ascii?Q?757QH1cr4e+e2SGJvsyISWGbTXXztws/lc8SrDnWH1c5Z7wqzazERC/rM2eb?= =?us-ascii?Q?VqABh7IGd590z2y8TQ2K2QkBb3T7zigOAU0RTDIVT0XI6kXFDoGpB9mK2PPu?= =?us-ascii?Q?fFnTS7GEFAvbmgrfjmYwysAOnb4NJRqLwYPu2rC6P6Ri0HYNCSJQ0JMTDum5?= =?us-ascii?Q?GC0ky+Ophw95bLcUXqfrthQecA+I7A+3ge5VHM5tQcwtVqohsbXskn7VICHX?= =?us-ascii?Q?2txmYnrCchcD1+R3A/VMA8+Ctpo+1lICxf0S6qStC315lG1ShzYw4b5o5hSg?= =?us-ascii?Q?OFeC+4E0G2vO1u0FTPfdO4HGsI+P8/kK7xrf4CTiwAoCwCTv2k+gMUaf0wun?= =?us-ascii?Q?ikPUuPXaObve/4IR8LdqddmYk4Q1ykGMI2PtfdgxjLzCByNpdALeXHvAy3Gk?= =?us-ascii?Q?+MMb8MKdgvRzf9ZgZYCEazbMqWzniLV5NLlYT7hKJxXF8LUlI+inTsDse7nZ?= =?us-ascii?Q?Crju2odhA+kH/VAV9GtSgYH05sviAC6FJp2HmwZ8oDhjgUZ1kUdjMP+9HKwk?= =?us-ascii?Q?uihp8SIcUFZIcbJzXOHqeNE+jBd/CCrHXg4zD0yOINyv5lGhYZXUgHkWTwlb?= =?us-ascii?Q?UkVASdgB5+08XqpPMCB08Y7htnc1Fo7eLLh/STLpcgeXsd7H6NtSZZD1BG8v?= =?us-ascii?Q?4vLDHIx4/ikBIdBw6f6H4UQW1JhUgZTe65tANdTVldB4DK+EAr0D3jshBGQR?= =?us-ascii?Q?ttKy1a6jGSYcQn53tAk8wlOx0b64sjta8eOWFx9aWx46z2JMqLXi4kE3JemJ?= =?us-ascii?Q?05PaE4Yj46ycmOAdC+86fh3q9UsA+lTFo0eDnX4B2g5kjshOYkLWaAQodfKi?= =?us-ascii?Q?jIYJh+5cG5lKEBrBQ8Rhp9/ToXahp/wzz8e9d3uRwE7CfcS9klH5VSyxk7W1?= =?us-ascii?Q?9VOpv87BuvttX2/GqAxlFEutLiXhohRcyj9Sgl2JoFfk96uVkFoCTDhPt5n/?= =?us-ascii?Q?WQ=3D=3D?= X-OriginatorOrg: memverge.com X-MS-Exchange-CrossTenant-Network-Message-Id: faf0ff5f-1d56-4bd4-e993-08daf9895131 X-MS-Exchange-CrossTenant-AuthSource: BN6PR17MB3121.namprd17.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Jan 2023 19:22:19.6751 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5c90cb59-37e7-4c81-9c07-00473d5fb682 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 9H3WKk9eDd5Ss/XQS0MIUv1GxxpzOwvJ7tdizMG6cJ9aFdMwS9M1IO0NhAJU6DylM7uKOzgXlorpi92G9a8miXLRlilMj1JzUgQQfQQeUwU= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR17MB3762 Received-SPF: none client-ip=2a01:111:f400:7ea9::629; envelope-from=gregory.price@memverge.com; helo=NAM02-SN1-obe.outbound.protection.outlook.com X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FORGED_SPF_HELO=1, SPF_HELO_PASS=-0.001, SPF_NONE=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org 1) No stack traces present 2) Device usage appears to work, but cxl-cli fails to create a region, i haven't checked why yet (also tried ndctl-75, same results) 3) There seems to be some other regression with the cxl_pmem_init routine, because I get a stack trace in this setup regardless of whether I apply the type-3 device commit. All tests below with the previously posted DOE linux branch. Base QEMU branch was Jonathan's 2023-1-11 DOE Branch - 2023-1-11 (HEAD) (all commits) QEMU Config: sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \ -drive file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd \ -m 3G,slots=4,maxmem=8G \ -smp 4 \ -machine type=q35,accel=kvm,cxl=on \ -enable-kvm \ -nographic \ -object memory-backend-ram,id=mem0,size=1G,share=on \ -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \ -device cxl-rp,id=rp0,bus=cxl.0,chassis=0,slot=0 \ -device cxl-type3,bus=rp0,volatile-memdev=mem0,id=cxl-mem0 \ -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G Result: This worked, but cxl-cli could not create a region (will look into this further later). When running with a persistent memory configuration, I'm seeing a kernel stack trace on cxl_pmem_init Config: sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \ -drive file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd \ -m 3G,slots=4,maxmem=4G \ -smp 4 \ -machine type=q35,accel=kvm,cxl=on \ -enable-kvm \ -nographic \ -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \ -device cxl-rp,port=0,id=rp0,bus=cxl.0,chassis=0,slot=0 \ -object memory-backend-file,id=cxl-mem0,mem-path=/tmp/mem0,size=1G \ -object memory-backend-file,id=cxl-lsa0,mem-path=/tmp/lsa0,size=1G \ -device cxl-type3,bus=rp0,persistent-memdev=cxl-mem0,lsa=cxl-lsa0,id=cxl-pmem0 \ -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G [ 62.167518] BUG: kernel NULL pointer dereference, address: 00000000000004c0 [ 62.185069] #PF: supervisor read access in kernel mode [ 62.198502] #PF: error_code(0x0000) - not-present page [ 62.211019] PGD 0 P4D 0 [ 62.220521] Oops: 0000 [#1] PREEMPT SMP PTI [ 62.233457] CPU: 3 PID: 558 Comm: systemd-udevd Not tainted 6.2.0-rc1+ #1 [ 62.252886] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.qemu.org 04/01/2014 [ 62.258432] Adding 2939900k swap on /dev/zram0. Priority:100 extents:1 across:2939900k SSDscFS [ 62.285513] RIP: 0010:cxl_nvdimm_probe+0x8d/0x130 [cxl_pmem] [ 62.285529] Code: 85 c0 0f 85 90 00 00 00 f0 80 0c 24 40 f0 80 4c 24 08 10 f0 80 4c 24 08 20 f0 80 4c 24 08 40 49 8d 84 24 b8 04 00 00 4c 89 0 [ 62.285531] RSP: 0018:ffffacff0141fc38 EFLAGS: 00010202 [ 62.285534] RAX: ffff97a8a37b84b8 RBX: ffff97a8a37b8000 RCX: 0000000000000000 [ 62.285536] RDX: 0000000000000001 RSI: ffff97a8a37b8000 RDI: 00000000ffffffff [ 62.285537] RBP: ffff97a8a37b8000 R08: 0000000000000001 R09: 0000000000000001 [ 62.285538] R10: 0000000000000001 R11: 0000000000000000 R12: ffff97a8a37b8000 [ 62.285539] R13: ffff97a982c3dc28 R14: 0000000000000000 R15: 0000000000000000 [ 62.285541] FS: 00007f2619829580(0000) GS:ffff97a9bca00000(0000) knlGS:0000000000000000 [ 62.285542] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 62.285544] CR2: 00000000000004c0 CR3: 00000001056a8000 CR4: 00000000000006e0 [ 62.285653] Call Trace: [ 62.285656] [ 62.285660] cxl_bus_probe+0x17/0x50 [ 62.285691] really_probe+0xde/0x380 [ 62.285695] ? pm_runtime_barrier+0x50/0x90 [ 62.285700] __driver_probe_device+0x78/0x170 [ 62.285846] driver_probe_device+0x1f/0x90 [ 62.285850] __driver_attach+0xd2/0x1c0 [ 62.285853] ? __pfx___driver_attach+0x10/0x10 [ 62.285856] bus_for_each_dev+0x76/0xa0 [ 62.285860] bus_add_driver+0x1b1/0x200 [ 62.285863] driver_register+0x89/0xe0 [ 62.285868] ? __pfx_init_module+0x10/0x10 [cxl_pmem] [ 62.285874] cxl_pmem_init+0x50/0xff0 [cxl_pmem] [ 62.285880] do_one_initcall+0x6e/0x330 [ 62.285888] do_init_module+0x4a/0x200 [ 62.285892] __do_sys_finit_module+0x93/0xf0 [ 62.285899] do_syscall_64+0x5b/0x80 [ 62.285904] ? do_syscall_64+0x67/0x80 [ 62.285906] ? asm_exc_page_fault+0x22/0x30 [ 62.285910] ? lockdep_hardirqs_on+0x7d/0x100 [ 62.285914] entry_SYSCALL_64_after_hwframe+0x72/0xdc [ 62.285917] RIP: 0033:0x7f2619b0afbd [ 62.285920] Code: 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 8 [ 62.285922] RSP: 002b:00007ffcc516bf58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 [ 62.285924] RAX: ffffffffffffffda RBX: 00005557c0dcaa60 RCX: 00007f2619b0afbd [ 62.285925] RDX: 0000000000000000 RSI: 00007f261a18743c RDI: 0000000000000006 [ 62.285926] RBP: 00007f261a18743c R08: 0000000000000000 R09: 00007f261a17bb52 [ 62.285927] R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000020000 [ 62.285928] R13: 00005557c0dbbce0 R14: 0000000000000000 R15: 00005557c0dc18a0 [ 62.285932] [ 62.285933] Modules linked in: cxl_pmem(+) snd_pcm libnvdimm snd_timer snd joydev bochs cxl_mem drm_vram_helper parport_pc soundcore drm_ttm_g [ 62.285954] CR2: 00000000000004c0 [ 62.288385] ---[ end trace 0000000000000000 ]--- [ 63.203514] RIP: 0010:cxl_nvdimm_probe+0x8d/0x130 [cxl_pmem] [ 63.203562] Code: 85 c0 0f 85 90 00 00 00 f0 80 0c 24 40 f0 80 4c 24 08 10 f0 80 4c 24 08 20 f0 80 4c 24 08 40 49 8d 84 24 b8 04 00 00 4c 89 0 [ 63.203565] RSP: 0018:ffffacff0141fc38 EFLAGS: 00010202 [ 63.203570] RAX: ffff97a8a37b84b8 RBX: ffff97a8a37b8000 RCX: 0000000000000000 [ 63.203572] RDX: 0000000000000001 RSI: ffff97a8a37b8000 RDI: 00000000ffffffff [ 63.203574] RBP: ffff97a8a37b8000 R08: 0000000000000001 R09: 0000000000000001 [ 63.203576] R10: 0000000000000001 R11: 0000000000000000 R12: ffff97a8a37b8000 [ 63.203577] R13: ffff97a982c3dc28 R14: 0000000000000000 R15: 0000000000000000 [ 63.203580] FS: 00007f2619829580(0000) GS:ffff97a9bca00000(0000) knlGS:0000000000000000 [ 63.203583] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 63.203585] CR2: 00000000000004c0 CR3: 00000001056a8000 CR4: 00000000000006e0 Next i reverted the QEMU branch to the commit just before the type-3 volatile commit and used the old method of launching with a type-3 pmem device Config: sudo /opt/qemu-cxl/bin/qemu-system-x86_64 \ -drive file=/var/lib/libvirt/images/cxl.qcow2,format=qcow2,index=0,media=disk,id=hd \ -m 2G,slots=4,maxmem=4G \ -smp 4 \ -machine type=q35,accel=kvm,cxl=on \ -enable-kvm \ -nographic \ -device pxb-cxl,id=cxl.0,bus=pcie.0,bus_nr=52 \ -device cxl-rp,id=rp0,bus=cxl.0,chassis=0,slot=0 \ -object memory-backend-file,pmem=true,id=cxl-mem0,mem-path=/tmp/cxl-mem0,size=1G \ -object memory-backend-file,pmem=true,id=lsa0,mem-path=/tmp/cxl-lsa0,size=1G \ -device cxl-type3,bus=rp0,memdev=cxl-mem0,lsa=lsa0,id=cxl-pmem0 \ -M cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.size=1G Result: Similar stack trace [ 29.850023] BUG: kernel NULL pointer dereference, address: 00000000000004c0 [ 29.882400] RIP: 0010:cxl_nvdimm_probe+0x8d/0x130 [cxl_pmem] [ 29.957485] Call Trace: [ 29.959067] [ 29.962176] cxl_bus_probe+0x17/0x50 [ 29.964940] really_probe+0xde/0x380 [ 29.969065] ? pm_runtime_barrier+0x50/0x90 [ 29.973419] __driver_probe_device+0x78/0x170 [ 29.977183] driver_probe_device+0x1f/0x90 [ 29.984212] __driver_attach+0xd2/0x1c0 [ 29.988463] ? __pfx___driver_attach+0x10/0x10 [ 29.992379] bus_for_each_dev+0x76/0xa0 [ 29.997040] bus_add_driver+0x1b1/0x200 [ 30.000368] driver_register+0x89/0xe0 [ 30.004579] ? __pfx_init_module+0x10/0x10 [cxl_pmem] [ 30.012403] cxl_pmem_init+0x50/0xff0 [cxl_pmem] [ 30.019394] do_one_initcall+0x6e/0x330 [ 30.024028] do_init_module+0x4a/0x200 [ 30.029243] __do_sys_finit_module+0x93/0xf0 [ 30.034943] do_syscall_64+0x5b/0x80 [ 30.039844] ? do_syscall_64+0x67/0x80 [ 30.045163] ? do_syscall_64+0x67/0x80 [ 30.049729] ? lock_release+0x14b/0x440 [ 30.054055] ? seqcount_lockdep_reader_access.constprop.0+0x82/0x90 [ 30.061039] ? lock_is_held_type+0xe8/0x140 [ 30.067625] ? do_syscall_64+0x67/0x80 [ 30.071909] ? lockdep_hardirqs_on+0x7d/0x100 [ 30.079037] ? do_syscall_64+0x67/0x80 [ 30.084537] ? do_syscall_64+0x67/0x80 [ 30.089091] ? do_syscall_64+0x67/0x80 [ 30.094174] ? lockdep_hardirqs_on+0x7d/0x100 [ 30.099224] entry_SYSCALL_64_after_hwframe+0x72/0xdc [ 30.104446] RIP: 0033:0x7f000550afbd