diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2020-07-27 16:09:47 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-07-27 17:02:09 +1000 |
| commit | 909adfc66b9a1db21b5e8733e9ebfa6cd5135d74 (patch) | |
| tree | 0a9ddb0f92da86b3694aebe4161e76b731a4465f /arch/powerpc/kernel/exceptions-64s.S | |
| parent | f0479c4bcbd92d1a457d4a43bcab79f29d11334a (diff) | |
powerpc/64s/hash: Fix hash_preload running with interrupts enabled
Commit 2f92447f9f96 ("powerpc/book3s64/hash: Use the pte_t address from the
caller") removed the local_irq_disable from hash_preload, but it was
required for more than just the page table walk: the hash pte busy bit is
effectively a lock which may be taken in interrupt context, and the local
update flag test must not be preempted before it's used.
This solves apparent lockups with perf interrupting __hash_page_64K. If
get_perf_callchain then also takes a hash fault on the same page while it
is already locked, it will loop forever taking hash faults, which looks like
this:
cpu 0x49e: Vector: 100 (System Reset) at [c00000001a4f7d70]
pc: c000000000072dc8: hash_page_mm+0x8/0x800
lr: c00000000000c5a4: do_hash_page+0x24/0x38
sp: c0002ac1cc69ac70
msr: 8000000000081033
current = 0xc0002ac1cc602e00
paca = 0xc00000001de1f280 irqmask: 0x03 irq_happened: 0x01
pid = 20118, comm = pread2_processe
Linux version 5.8.0-rc6-00345-g1fad14f18bc6
49e:mon> t
[c0002ac1cc69ac70] c00000000000c5a4 do_hash_page+0x24/0x38 (unreliable)
--- Exception: 300 (Data Access) at c00000000008fa60 __copy_tofrom_user_power7+0x20c/0x7ac
[link register ] c000000000335d10 copy_from_user_nofault+0xf0/0x150
[c0002ac1cc69af70] c00032bf9fa3c880 (unreliable)
[c0002ac1cc69afa0] c000000000109df0 read_user_stack_64+0x70/0xf0
[c0002ac1cc69afd0] c000000000109fcc perf_callchain_user_64+0x15c/0x410
[c0002ac1cc69b060] c000000000109c00 perf_callchain_user+0x20/0x40
[c0002ac1cc69b080] c00000000031c6cc get_perf_callchain+0x25c/0x360
[c0002ac1cc69b120] c000000000316b50 perf_callchain+0x70/0xa0
[c0002ac1cc69b140] c000000000316ddc perf_prepare_sample+0x25c/0x790
[c0002ac1cc69b1a0] c000000000317350 perf_event_output_forward+0x40/0xb0
[c0002ac1cc69b220] c000000000306138 __perf_event_overflow+0x88/0x1a0
[c0002ac1cc69b270] c00000000010cf70 record_and_restart+0x230/0x750
[c0002ac1cc69b620] c00000000010d69c perf_event_interrupt+0x20c/0x510
[c0002ac1cc69b730] c000000000027d9c performance_monitor_exception+0x4c/0x60
[c0002ac1cc69b750] c00000000000b2f8 performance_monitor_common_virt+0x1b8/0x1c0
--- Exception: f00 (Performance Monitor) at c0000000000cb5b0 pSeries_lpar_hpte_insert+0x0/0x160
[link register ] c0000000000846f0 __hash_page_64K+0x210/0x540
[c0002ac1cc69ba50] 0000000000000000 (unreliable)
[c0002ac1cc69bb00] c000000000073ae0 update_mmu_cache+0x390/0x3a0
[c0002ac1cc69bb70] c00000000037f024 wp_page_copy+0x364/0xce0
[c0002ac1cc69bc20] c00000000038272c do_wp_page+0xdc/0xa60
[c0002ac1cc69bc70] c0000000003857bc handle_mm_fault+0xb9c/0x1b60
[c0002ac1cc69bd50] c00000000006c434 __do_page_fault+0x314/0xc90
[c0002ac1cc69be20] c00000000000c5c8 handle_page_fault+0x10/0x2c
--- Exception: 300 (Data Access) at 00007fff8c861fe8
SP (7ffff6b19660) is in userspace
Fixes: 2f92447f9f96 ("powerpc/book3s64/hash: Use the pte_t address from the caller")
Reported-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reported-by: Anton Blanchard <anton@ozlabs.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200727060947.10060-1-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kernel/exceptions-64s.S')
| -rw-r--r-- | arch/powerpc/kernel/exceptions-64s.S | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 0fc8bad878b2..446e54c3f71e 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -3072,10 +3072,18 @@ do_hash_page: ori r0,r0,DSISR_BAD_FAULT_64S@l and. r0,r5,r0 /* weird error? */ bne- handle_page_fault /* if not, try to insert a HPTE */ + + /* + * If we are in an "NMI" (e.g., an interrupt when soft-disabled), then + * don't call hash_page, just fail the fault. This is required to + * prevent re-entrancy problems in the hash code, namely perf + * interrupts hitting while something holds H_PAGE_BUSY, and taking a + * hash fault. See the comment in hash_preload(). + */ ld r11, PACA_THREAD_INFO(r13) - lwz r0,TI_PREEMPT(r11) /* If we're in an "NMI" */ - andis. r0,r0,NMI_MASK@h /* (i.e. an irq when soft-disabled) */ - bne 77f /* then don't call hash_page now */ + lwz r0,TI_PREEMPT(r11) + andis. r0,r0,NMI_MASK@h + bne 77f /* * r3 contains the trap number |