s390/ap: fix AP bus crash on early config change callback invocation

hfreude · Vasily Gorbik · commit e14aec23025e · 2023-11-05T22:34:57.000+01:00
Fix kernel crash in AP bus code caused by very early invocation of the config change callback function via SCLP. After a fresh IML of the machine the crypto cards are still offline and will get switched online only with activation of any LPAR which has the card in it's configuration. A crypto card coming online is reported to the LPAR via SCLP and the AP bus offers a callback function to get this kind of information. However, it may happen that the callback is invoked before the AP bus init function is complete. As the callback triggers a synchronous AP bus scan, the scan may already run but some internal states are not initialized by the AP bus init function resulting in a crash like this: [ 11.635859] Unable to handle kernel pointer dereference in virtual kernel address space [ 11.635861] Failing address: 0000000000000000 TEID: 0000000000000887 [ 11.635862] Fault in home space mode while using kernel ASCE. [ 11.635864] AS:00000000894c4007 R3:00000001fece8007 S:00000001fece7800 P:000000000000013d [ 11.635879] Oops: 0004 ilc:1 [#1] SMP [ 11.635882] Modules linked in: [ 11.635884] CPU: 5 PID: 42 Comm: kworker/5:0 Not tainted 6.6.0-rc3-00003-g4dbf7cdc6b42 #12 [ 11.635886] Hardware name: IBM 3931 A01 751 (LPAR) [ 11.635887] Workqueue: events_long ap_scan_bus [ 11.635891] Krnl PSW : 0704c00180000000 0000000000000000 (0x0) [ 11.635895] R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 [ 11.635897] Krnl GPRS: 0000000001000a00 0000000000000000 0000000000000006 0000000089591940 [ 11.635899] 0000000080000000 0000000000000a00 0000000000000000 0000000000000000 [ 11.635901] 0000000081870c00 0000000089591000 000000008834e4e2 0000000002625a00 [ 11.635903] 0000000081734200 0000038000913c18 000000008834c6d6 0000038000913ac8 [ 11.635906] Krnl Code:>0000000000000000: 0000 illegal [ 11.635906] 0000000000000002: 0000 illegal [ 11.635906] 0000000000000004: 0000 illegal [ 11.635906] 0000000000000006: 0000 illegal [ 11.635906] 0000000000000008: 0000 illegal [ 11.635906] 000000000000000a: 0000 illegal [ 11.635906] 000000000000000c: 0000 illegal [ 11.635906] 000000000000000e: 0000 illegal [ 11.635915] Call Trace: [ 11.635916] [<0000000000000000>] 0x0 [ 11.635918] [<000000008834e4e2>] ap_queue_init_state+0x82/0xb8 [ 11.635921] [<000000008834ba1c>] ap_scan_domains+0x6fc/0x740 [ 11.635923] [<000000008834c092>] ap_scan_adapter+0x632/0x8b0 [ 11.635925] [<000000008834c3e4>] ap_scan_bus+0xd4/0x288 [ 11.635927] [<00000000879a33ba>] process_one_work+0x19a/0x410 [ 11.635930] Discipline DIAG cannot be used without z/VM [ 11.635930] [<00000000879a3a2c>] worker_thread+0x3fc/0x560 [ 11.635933] [<00000000879aea60>] kthread+0x120/0x128 [ 11.635936] [<000000008792afa4>] __ret_from_fork+0x3c/0x58 [ 11.635938] [<00000000885ebe62>] ret_from_fork+0xa/0x30 [ 11.635942] Last Breaking-Event-Address: [ 11.635942] [<000000008834c6d4>] ap_wait+0xcc/0x148 This patch improves the ap_bus_force_rescan() function which is invoked by the config change callback by checking if a first initial AP bus scan has been done. If not, the force rescan request is simple ignored. Anyhow it does not make sense to trigger AP bus re-scans even before the very first bus scan is complete. Cc: stable@vger.kernel.org Reviewed-by: Holger Dengler <dengler@linux.ibm.com> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c
@@ -1022,6 +1022,10 @@ EXPORT_SYMBOL(ap_driver_unregister);
 
 void ap_bus_force_rescan(void)
 {
+	/* Only trigger AP bus scans after the initial scan is done */
+	if (atomic64_read(&ap_scan_bus_count) <= 0)
+		return;
+
 	/* processing a asynchronous bus rescan */
 	del_timer(&ap_config_timer);
 	queue_work(system_long_wq, &ap_scan_work);
