| From 60f1bf29c0b2519989927cae640cd1f50f59dc7f Mon Sep 17 00:00:00 2001 |
| From: David Hildenbrand <david@redhat.com> |
| Date: Fri, 11 Jan 2019 15:18:22 +0100 |
| Subject: s390/smp: Fix calling smp_call_ipl_cpu() from ipl CPU |
| |
| From: David Hildenbrand <david@redhat.com> |
| |
| commit 60f1bf29c0b2519989927cae640cd1f50f59dc7f upstream. |
| |
| When calling smp_call_ipl_cpu() from the IPL CPU, we will try to read |
| from pcpu_devices->lowcore. However, due to prefixing, that will result |
| in reading from absolute address 0 on that CPU. We have to go via the |
| actual lowcore instead. |
| |
| This means that right now, we will read lc->nodat_stack == 0 and |
| therfore work on a very wrong stack. |
| |
| This BUG essentially broke rebooting under QEMU TCG (which will report |
| a low address protection exception). And checking under KVM, it is |
| also broken under KVM. With 1 VCPU it can be easily triggered. |
| |
| :/# echo 1 > /proc/sys/kernel/sysrq |
| :/# echo b > /proc/sysrq-trigger |
| [ 28.476745] sysrq: SysRq : Resetting |
| [ 28.476793] Kernel stack overflow. |
| [ 28.476817] CPU: 0 PID: 424 Comm: sh Not tainted 5.0.0-rc1+ #13 |
| [ 28.476820] Hardware name: IBM 2964 NE1 716 (KVM/Linux) |
| [ 28.476826] Krnl PSW : 0400c00180000000 0000000000115c0c (pcpu_delegate+0x12c/0x140) |
| [ 28.476861] R:0 T:1 IO:0 EX:0 Key:0 M:0 W:0 P:0 AS:3 CC:0 PM:0 RI:0 EA:3 |
| [ 28.476863] Krnl GPRS: ffffffffffffffff 0000000000000000 000000000010dff8 0000000000000000 |
| [ 28.476864] 0000000000000000 0000000000000000 0000000000ab7090 000003e0006efbf0 |
| [ 28.476864] 000000000010dff8 0000000000000000 0000000000000000 0000000000000000 |
| [ 28.476865] 000000007fffc000 0000000000730408 000003e0006efc58 0000000000000000 |
| [ 28.476887] Krnl Code: 0000000000115bfe: 4170f000 la %r7,0(%r15) |
| [ 28.476887] 0000000000115c02: 41f0a000 la %r15,0(%r10) |
| [ 28.476887] #0000000000115c06: e370f0980024 stg %r7,152(%r15) |
| [ 28.476887] >0000000000115c0c: c0e5fffff86e brasl %r14,114ce8 |
| [ 28.476887] 0000000000115c12: 41f07000 la %r15,0(%r7) |
| [ 28.476887] 0000000000115c16: a7f4ffa8 brc 15,115b66 |
| [ 28.476887] 0000000000115c1a: 0707 bcr 0,%r7 |
| [ 28.476887] 0000000000115c1c: 0707 bcr 0,%r7 |
| [ 28.476901] Call Trace: |
| [ 28.476902] Last Breaking-Event-Address: |
| [ 28.476920] [<0000000000a01c4a>] arch_call_rest_init+0x22/0x80 |
| [ 28.476927] Kernel panic - not syncing: Corrupt kernel stack, can't continue. |
| [ 28.476930] CPU: 0 PID: 424 Comm: sh Not tainted 5.0.0-rc1+ #13 |
| [ 28.476932] Hardware name: IBM 2964 NE1 716 (KVM/Linux) |
| [ 28.476932] Call Trace: |
| |
| Fixes: 2f859d0dad81 ("s390/smp: reduce size of struct pcpu") |
| Cc: stable@vger.kernel.org # 4.0+ |
| Reported-by: Cornelia Huck <cohuck@redhat.com> |
| Signed-off-by: David Hildenbrand <david@redhat.com> |
| Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| |
| --- |
| arch/s390/kernel/smp.c | 8 ++++++-- |
| 1 file changed, 6 insertions(+), 2 deletions(-) |
| |
| --- a/arch/s390/kernel/smp.c |
| +++ b/arch/s390/kernel/smp.c |
| @@ -387,9 +387,13 @@ void smp_call_online_cpu(void (*func)(vo |
| */ |
| void smp_call_ipl_cpu(void (*func)(void *), void *data) |
| { |
| + struct lowcore *lc = pcpu_devices->lowcore; |
| + |
| + if (pcpu_devices[0].address == stap()) |
| + lc = &S390_lowcore; |
| + |
| pcpu_delegate(&pcpu_devices[0], func, data, |
| - pcpu_devices->lowcore->panic_stack - |
| - PANIC_FRAME_OFFSET + PAGE_SIZE); |
| + lc->panic_stack - PANIC_FRAME_OFFSET + PAGE_SIZE); |
| } |
| |
| int smp_find_processor_id(u16 address) |