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pr=C From: Stewart Hildebrand To: CC: Stewart Hildebrand , George Dunlap , Dario Faggioli , "Juergen Gross" Subject: [PATCH v1] xen/sched/null: avoid crash after failed domU creation Date: Mon, 1 May 2023 16:30:46 -0400 Message-ID: <20230501203046.168856-1-stewart.hildebrand@amd.com> X-Mailer: git-send-email 2.40.1 MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS1PEPF0000E649:EE_|SA3PR12MB7784:EE_ X-MS-Office365-Filtering-Correlation-Id: d80ca6cd-7382-4db1-4971-08db4a82f387 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:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB03.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230028)(4636009)(396003)(39860400002)(136003)(346002)(376002)(451199021)(36840700001)(46966006)(40470700004)(40480700001)(40460700003)(316002)(1076003)(82310400005)(26005)(426003)(336012)(41300700001)(2616005)(47076005)(83380400001)(186003)(478600001)(70206006)(36860700001)(54906003)(70586007)(4326008)(966005)(6916009)(356005)(82740400003)(81166007)(36756003)(2906002)(5660300002)(86362001)(8936002)(8676002)(44832011)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 May 2023 20:30:49.4209 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d80ca6cd-7382-4db1-4971-08db4a82f387 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: DS1PEPF0000E649.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB7784 When creating a domU, but the creation fails, there is a corner case that may lead to a crash in the null scheduler when running a debug build of Xen. (XEN) **************************************** (XEN) Panic on CPU 0: (XEN) Assertion 'npc->unit == unit' failed at common/sched/null.c:379 (XEN) **************************************** The events leading to the crash are: * null_unit_insert() was invoked with the unit offline. Since the unit was offline, unit_assign() was not called, and null_unit_insert() returned. * Later during domain creation, the unit was onlined * Eventually, domain creation failed due to bad configuration * null_unit_remove() was invoked with the unit still online. Since the unit was online, it called unit_deassign() and triggered an ASSERT. To fix this, only call unit_deassign() when npc->unit is non-NULL in null_unit_remove. Signed-off-by: Stewart Hildebrand Reviewed-by: Juergen Gross Acked-by: Dario Faggioli --- RFC->v1 * Follow Juergen's suggested fix Link to RFC [1] [1] https://lists.xenproject.org/archives/html/xen-devel/2023-04/msg01387.html --- xen/common/sched/null.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/xen/common/sched/null.c b/xen/common/sched/null.c index 65a0a6c5312d..2091337fcd06 100644 --- a/xen/common/sched/null.c +++ b/xen/common/sched/null.c @@ -522,6 +522,8 @@ static void cf_check null_unit_remove( { struct null_private *prv = null_priv(ops); struct null_unit *nvc = null_unit(unit); + struct null_pcpu *npc; + unsigned int cpu; spinlock_t *lock; ASSERT(!is_idle_unit(unit)); @@ -531,8 +533,6 @@ static void cf_check null_unit_remove( /* If offline, the unit shouldn't be assigned, nor in the waitqueue */ if ( unlikely(!is_unit_online(unit)) ) { - struct null_pcpu *npc; - npc = unit->res->sched_priv; ASSERT(npc->unit != unit); ASSERT(list_empty(&nvc->waitq_elem)); @@ -549,7 +549,10 @@ static void cf_check null_unit_remove( goto out; } - unit_deassign(prv, unit); + cpu = sched_unit_master(unit); + npc = get_sched_res(cpu)->sched_priv; + if ( npc->unit ) + unit_deassign(prv, unit); out: unit_schedule_unlock_irq(lock, unit);