Re: [PATCH] powerpc/pseries: Fix scv instruction crash with kexec

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 26/06/24 15:10, Gautam Menghani wrote:
> Without this patch, we had an issue where if we have some cpus disabled
> in the system and we try to do a 2 stage kexec as follows:
>
> kexec -l vmlinux ....
> kexec -e
>
> we would hit the following Oops
>
> [ 2598.923098] kernel BUG at arch/powerpc/kernel/exceptions-64s.S:501!
> [ 2598.923103] Oops: Exception in kernel mode, sig: 5 [#1]
> [ 2598.923107] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
> [ 2598.923111] Modules linked in: rpcrdma rdma_cm iw_cm ib_cm ib_core xt_CHECKSUM xt_MASQUERADE xt_conntrack ipt_REJECT nf_reject_ipv4 nft_compat nft_chain_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables bridge stp llc kvm_hv kvm bonding tls rfkill binfmt_misc tg3 vmx_crypto aes_gcm_p10_crypto ibmveth crct10dif_vpmsum pseries_rng nfsd auth_rpcgss nfs_acl lockd grace sunrpc fuse loop dm_multipath nfnetlink zram xfs ibmvscsi scsi_transport_srp crc32c_vpmsum pseries_wdt scsi_dh_rdac scsi_dh_emc scsi_dh_alua ip6_tables ip_tables
> [ 2598.923167] CPU: 11 PID: 1548 Comm: systemd-journal Not tainted 6.9.0+ #4
> [ 2598.923171] Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_022) hv:phyp pSeries
> [ 2598.923176] NIP:  c0000000000089e4 LR: 00007fffaa1427c4 CTR: c0000000000089b0
> [ 2598.923180] REGS: c0000008dfe7fd60 TRAP: 0700   Not tainted  (6.9.0+)
> [ 2598.923184] MSR:  8000000000021031 <SF,ME,IR,DR,LE>  CR: 28002413  XER: 00000000
> [ 2598.923192] CFAR: c0000000000089dc IRQMASK: 0
> [ 2598.923192] GPR00: 0000000000000003 00007ffff40fb110 0000000000000000 0000000000000009
> [ 2598.923192] GPR04: 00007ffff40fbcf0 0000000000002000 00007ffff40fdcc0 0000000000000000
> [ 2598.923192] GPR08: 00007fffaabc3b80 0000000048002413 00007ffff40fb3e0 0000000000017000
> [ 2598.923192] GPR12: 8000000000009003 c0000008dfff2b00 0000000000000000 0000000000000000
> [ 2598.923192] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [ 2598.923192] GPR20: 0000000000000000 0000000000000000 0000000000000000 00007fffaabaf448
> [ 2598.923192] GPR24: 000000011bc72700 00007ffff40fddf8 0000000132490ea0 00007ffff40fddf0
> [ 2598.923192] GPR28: 0000000000000000 00007ffff40fbcf0 0000000000002000 0000000000000009
> [ 2598.923238] NIP [c0000000000089e4] data_access_common_virt+0x14/0x220
> [ 2598.923245] LR [00007fffaa1427c4] 0x7fffaa1427c4
> [ 2598.923251] Call Trace:
> [ 2598.923253] Code: 2c0a0000 39400300 408242c0 e94d0020 694a0002 7d400164 60420000 718a4000 7c2a0b78 3821fd30 41c20008 e82d0910 <0981fd30> f9210160 f9610130 f9810138
> [ 2598.923269] ---[ end trace 0000000000000000 ]---
> [ 2598.926662] pstore: backend (nvram) writing error (-1)
>
>
> With this patch, the disabled cpus are woken up and kexec goes through
> fine.

Verified the same on LPAR and has similar observation as Guatam 
mentioned above.

Thanks for the fix Nick.

Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>

- Sourabh