linux-kernel - Re: [mainline] Kernel OOPs while running powerpc/mce/ selftest

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Message-ID: <18dd8200-6a8c-449e-9fb8-56874342defb@csgroup.eu>
Date: Wed, 5 Nov 2025 14:45:40 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Venkat Rao Bagalkote <venkat88@...ux.ibm.com>,
 linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
 LKML <linux-kernel@...r.kernel.org>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Ganesh Goudar <ganeshgr@...ux.ibm.com>, Nathan Lynch <nathanl@...ux.ibm.com>
Subject: Re: [mainline] Kernel OOPs while running powerpc/mce/ selftest



Le 23/10/2025 à 06:54, Venkat Rao Bagalkote a écrit :
> Greetings!!!
> 
> 
> IBM CI has reported a kernel crash while running mce selftests on 
> mainline kernel, from tools/testing/selftests/powerpc/mce/.
> 
> 
> This issue is hit when CONFIG_KASAN is enabled. If its disabled, test 
> passes.
> 
> 
> Traces:
> 
> 
> [ 8041.225432] BUG: Unable to handle kernel data access on read at 
> 0xc00e0001a1ad6103
> [ 8041.225453] Faulting instruction address: 0xc0000000008c54d8
> [ 8041.225461] Oops: Kernel access of bad area, sig: 11 [#1]
> [ 8041.225467] LE PAGE_SIZE=64K MMU=Radix  SMP NR_CPUS=8192 NUMA pSeries
> [ 8041.225475] Modules linked in: nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 
> nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct 
> nft_chain_nat nf_nat nf_conntrack bonding tls nf_defrag_ipv6 
> nf_defrag_ipv4 rfkill ip_set nf_tables nfnetlink pseries_rng vmx_crypto 
> dax_pmem fuse ext4 crc16 mbcache jbd2 nd_pmem papr_scm sd_mod libnvdimm 
> sg ibmvscsi ibmveth scsi_transport_srp pseries_wdt
> [ 8041.225558] CPU: 17 UID: 0 PID: 877869 Comm: inject-ra-err Kdump: 
> loaded Not tainted 6.18.0-rc2+ #1 VOLUNTARY
> [ 8041.225569] Hardware name: IBM,9080-HEX Power11 (architected) 
> 0x820200 0xf000007 of:IBM,FW1110.01 (NH1110_069) hv:phyp pSeries
> [ 8041.225576] NIP:  c0000000008c54d8 LR: c00000000004e464 CTR: 
> 0000000000000000
> [ 8041.225583] REGS: c0000000fff778d0 TRAP: 0300   Not tainted (6.18.0- 
> rc2+)
> [ 8041.225590] MSR:  8000000000001003 <SF,ME,RI,LE>  CR: 48002828  XER: 
> 00000000
> [ 8041.225607] CFAR: c00000000004e460 DAR: c00e0001a1ad6103 DSISR: 
> 40000000 IRQMASK: 3
> [ 8041.225607] GPR00: c0000000019d0598 c0000000fff77b70 c00000000244a400 
> c000000d0d6b0818
> [ 8041.225607] GPR04: 0000000000004d43 0000000000000008 c00000000004e464 
> 004d424900000000
> [ 8041.225607] GPR08: 0000000000000001 18000001a1ad6103 a80e000000000000 
> 0000000003000048
> [ 8041.225607] GPR12: 0000000000000000 c000000d0ddf3300 0000000000000000 
> 0000000000000000
> [ 8041.225607] GPR16: 0000000000000000 0000000000000000 0000000000000000 
> 0000000000000000
> [ 8041.225607] GPR20: 0000000000000000 0000000000000000 0000000000000000 
> 0000000000000000
> [ 8041.225607] GPR24: 0000000000000000 0000000000000000 0000000000000000 
> 0000000000000000
> [ 8041.225607] GPR28: c000000d0d6b0888 c000000d0d6b0800 0000000000004d43 
> c000000d0d6b0818
> [ 8041.225701] NIP [c0000000008c54d8] __asan_load2+0x54/0xd8
> [ 8041.225712] LR [c00000000004e464] pseries_errorlog_id+0x20/0x3c
> [ 8041.225722] Call Trace:
> [ 8041.225726] [c0000000fff77b90] [c0000000001f8748] 
> fwnmi_get_errinfo+0xd4/0x104
> [ 8041.225738] [c0000000fff77bc0] [c0000000019d0598] 
> get_pseries_errorlog+0xa8/0x110
> [ 8041.225750] [c0000000fff77c00] [c0000000001f8f68] 
> pseries_machine_check_realmode+0x11c/0x214
> [ 8041.225762] [c0000000fff77ce0] [c000000000049ca4] 
> machine_check_early+0x74/0xc0
> [ 8041.225771] [c0000000fff77d30] [c0000000000084a4] 
> machine_check_early_common+0x1b4/0x2c0

Is it a new problem or has it always been there ?

The problem is because KASAN is not compatible with realmode (MMU 
translation is OFF).

pseries_machine_check_realmode() is located in 
arch/powerpc/platforms/pseries/ras.c built with KASAN_SANITIZE_ras.o := n

But pseries_machine_check_realmode() calls mce_handle_error() which 
calls get_pseries_errorlog().

get_pseries_errorlog() is in arch/powerpc/kernel/rtas.c which is _not_ 
built with KASAN_SANITIZE disabled hence the Oops.

Unrelated, but it looks like there is also a problem with commit 
cc15ff327569 ("powerpc/mce: Avoid using irq_work_queue() in realmode"), 
which removed the re-enabling of translation but left the call to 
mce_handle_err_virtmode().

Christophe