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X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Jun 2025 21:43:25.4382 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0448a32d-cc82-46dc-c99b-08ddad1ed2ec 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=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: SJ1PEPF00002327.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA1PR12MB6994 Content-Type: text/plain; charset="utf-8" From: Ashish Kalra Panic notifiers are invoked with RCU read lock held and when the SNP panic notifier tries to unregister itself from the panic notifier callback itself it causes a deadlock as notifier unregistration does RCU synchronization. Code flow for SNP panic notifier: snp_shutdown_on_panic() -> __sev_firmware_shutdown() -> __sev_snp_shutdown_locked() -> atomic_notifier_chain_unregister(.., &snp_panic_notifier) Fix SNP panic notifier to unregister itself during SNP shutdown only if panic is not in progress. Reviewed-by: Tom Lendacky Fixes: 19860c3274fb ("crypto: ccp - Register SNP panic notifier only if SNP= is enabled") Signed-off-by: Ashish Kalra --- drivers/crypto/ccp/sev-dev.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c index 8fb94c5f006a..17edc6bf5622 100644 --- a/drivers/crypto/ccp/sev-dev.c +++ b/drivers/crypto/ccp/sev-dev.c @@ -1787,8 +1787,14 @@ static int __sev_snp_shutdown_locked(int *error, boo= l panic) sev->snp_initialized =3D false; dev_dbg(sev->dev, "SEV-SNP firmware shutdown\n"); =20 - atomic_notifier_chain_unregister(&panic_notifier_list, - &snp_panic_notifier); + /* + * __sev_snp_shutdown_locked() deadlocks when it tries to unregister + * itself during panic as the panic notifier is called with RCU read + * lock held and notifier unregistration does RCU synchronization. + */ + if (!panic) + atomic_notifier_chain_unregister(&panic_notifier_list, + &snp_panic_notifier); =20 /* Reset TMR size back to default */ sev_es_tmr_size =3D SEV_TMR_SIZE; --=20 2.34.1