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mx.microsoft.com 1; spf=pass smtp.mailfrom=arm.com; dmarc=pass action=none header.from=arm.com; dkim=pass header.d=arm.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=armh.onmicrosoft.com; s=selector2-armh-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=LOaFZqw/94qy9TlAD5tyDSboUXLAWK6+zX2L7IxX6dE=; b=anJUY5wh6o1S6iMtKPSFO/ById3hlWXKvKM3Eyjxmpf3LjDGvBrG79/ZL9V9N//NGx5+TF+8Pim6/Qe2+8e38NS50jh5LKAnKmXaHd163NRz4FCbz9mrsmtKwFtq1eER5ARgbJXpoPlY+94ytAadvJHm/b5mXMu8akPNnQ/bk88= Authentication-Results-Original: suse.com; dkim=none (message not signed) header.d=none;suse.com; dmarc=none action=none header.from=arm.com; Content-Type: text/plain; charset=utf-8 Subject: Re: xen/evtchn: Dom0 boot hangs using preempt_rt kernel 5.10 From: Luca Fancellu In-Reply-To: Date: Thu, 18 Mar 2021 08:47:07 +0000 Cc: "xen-devel@lists.xenproject.org" , "jgrall@amazon.com" Content-Transfer-Encoding: quoted-printable Message-Id: References: To: =?utf-8?B?SsO8cmdlbiBHcm/Dnw==?= X-Mailer: Apple Mail (2.3654.60.0.2.21) X-Originating-IP: [82.8.129.65] X-ClientProxiedBy: LO4P123CA0069.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:153::20) To VI1PR08MB3629.eurprd08.prod.outlook.com (2603:10a6:803:7f::25) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-HT: Tenant X-MS-Office365-Filtering-Correlation-Id: b9c4a6b2-629f-4fe8-cbe9-08d8e9ea73d5 X-MS-TrafficTypeDiagnostic: VE1PR08MB5661:|PR3PR08MB5676: X-Microsoft-Antispam-PRVS: x-checkrecipientrouted: true NoDisclaimer: true X-MS-Oob-TLC-OOBClassifiers: OLM:8882;OLM:8882; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Mar 2021 08:47:24.7815 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: b9c4a6b2-629f-4fe8-cbe9-08d8e9ea73d5 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT022.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PR3PR08MB5676 Hi Juergen, If you are willing to do the patch I think it will be faster to being accep= ted, what about the BUG_ON(=E2=80=A6) in evtchn_2l_unmask from events_2l.c = file? Cheers, Luca > On 18 Mar 2021, at 07:54, J=C3=BCrgen Gro=C3=9F wrote: >=20 > On 17.03.21 15:32, Luca Fancellu wrote: >> Hi all, >> we've been encountering an issue when using the kernel 5.10 with preempt= _rt support for Dom0, the problem is that during the boot of Dom0, it hits = a BUG_ON(!irqs_disabled()) from the function evtchn_fifo_unmask defined in = events_fifo.c. >> This is the call stack: >> [ 17.817018] ------------[ cut here ]------------ >> [ 17.817021] kernel BUG at drivers/xen/events/events_fifo.c:258! >> [ 18.817079] Internal error: Oops - BUG: 0 [#1] PREEMPT_RT SMP >> [ 18.817081] Modules linked in: bridge stp llc ipv6 >> [ 18.817086] CPU: 3 PID: 558 Comm: xenstored Not tainted 5.10.16-rt25-= yocto-preempt-rt #1 >> [ 18.817089] Hardware name: Arm Neoverse N1 System Development Platfor= m (DT) >> [ 18.817090] pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=3D--) >> [ 18.817092] pc : evtchn_fifo_unmask+0xd4/0xe0 >> [ 18.817099] lr : xen_irq_lateeoi_locked+0xec/0x200 >> [ 18.817102] sp : ffff8000123f3cc0 >> [ 18.817102] x29: ffff8000123f3cc0 x28: ffff0000427b1d80 >> [ 18.817104] x27: 0000000000000000 x26: 0000000000000000 >> [ 18.817106] x25: 0000000000000001 x24: 0000000000000001 >> [ 18.817107] x23: ffff0000412fc900 x22: 0000000000000004 >> [ 18.817109] x21: 0000000000000000 x20: ffff000042e06990 >> [ 18.817110] x19: ffff0000427b1d80 x18: 0000000000000010 >> [ 18.817112] x17: 0000000000000000 x16: 0000000000000000 >> [ 18.817113] x15: 0000000000000002 x14: 0000000000000001 >> [ 18.817114] x13: 000000000001a7e8 x12: 0000000000000040 >> [ 18.817116] x11: ffff000040400248 x10: ffff00004040024a >> [ 18.817117] x9 : ffff800011be5200 x8 : ffff000040400270 >> [ 18.817119] x7 : 0000000000000000 x6 : 0000000000000003 >> [ 18.817120] x5 : 0000000000000000 x4 : ffff000040400308 >> [ 18.817121] x3 : ffff0000408a400c x2 : 0000000000000000 >> [ 18.817122] x1 : 0000000000000000 x0 : ffff0000408a4000 >> [ 18.817124] Call trace: >> [ 18.817125] evtchn_fifo_unmask+0xd4/0xe0 >> [ 18.817127] xen_irq_lateeoi_locked+0xec/0x200 >> [ 18.817129] xen_irq_lateeoi+0x48/0x64 >> [ 18.817131] evtchn_write+0x124/0x15c >> [ 18.817134] vfs_write+0xf0/0x2cc >> [ 18.817137] ksys_write+0xe0/0x100 >> [ 18.817139] __arm64_sys_write+0x20/0x30 >> [ 18.817142] el0_svc_common.constprop.0+0x78/0x1a0 >> [ 18.817145] do_el0_svc+0x24/0x90 >> [ 18.817147] el0_svc+0x14/0x20 >> [ 18.817151] el0_sync_handler+0x1a4/0x1b0 >> [ 18.817153] el0_sync+0x174/0x180 >> [ 18.817156] Code: 52800120 b90023e6 97e6d104 17fffff0 (d4210000) >> [ 18.817158] ---[ end trace 0000000000000002 ]--- >> Our last tested kernel was the 5.4 and our analysis pointed out that the= introduction of the lateeoi framework (xen/events: add a new "late EOI" ev= tchn framework) in conjunction with the preempt_rt patches (irqs kept enabl= ed between spinlock_t/rwlock_t _irqsave///=E2=80=8B_irqrestore operations) = is the root cause. >> Given that many modifications were made to the mask/unmask operations, a= big one from Juergen Gross (xen/events: don't unmask an event channel when= an eoi is pending), is the BUG_ON(...) still needed? >> With the mentioned commit every call to a mask/unmask operation is prote= cted by a spinlock, so I would like to have some feedbacks from who has mor= e experience than me on this part of the code. >=20 > I think this BUG_ON() can be removed. >=20 > Are you planning to send a patch? >=20 >=20 > Juergen >