Re: [PATCH v4 0/5] Add support for the ARMv8.2 Statistical Profiling Extension

[Mark Rutland]

On Wed, Jun 28, 2017 at 12:26:02PM +0100, Mark Rutland wrote:
> On Tue, Jun 27, 2017 at 04:07:58PM -0500, Kim Phillips wrote:
> > FWIW, there is also this one I saw with mmap-pages set to 5
> > (pages), which gets rounded up to 8 pages:
> 
> Sorry, *what* does the rounding upwards? Userspace, perf core, or the
> driver? Where?
> 
> > the driver started memsetting places it shouldn't?:
> >
> > $ sudo ./perf record -c 512 -C 0 -e arm_spe/branch_filter=0,ts_enable=1,pa_enable=1,event_filter=0,load_filter=0,jitter=1,store_filter=0,min_latency=0/ --mmap-pages=,5 dd if=/dev/urandom of=/dev/null count=10000
> > rounding mmap pages size to 32K (8 pages)
> > 10000+0 records in
> > 10000+0 records out
> > 5120000 bytes (5.1 MB) copied, 1.3391 s, 3.8 MB/s
> > [ 1885.042803] Unable to handle kernel paging request at virtual address ffff00000adac000
> > [ 1885.042873] pgd = ffff00000ad48000
> > [ 1885.042899] [ffff00000adac000] *pgd=00000000fdffe003, *pud=00000000fdffd003, *pmd=00000000fdff8003, *pte=0000000000000000
> > [ 1885.043083] Internal error: Oops: 96000047 [#1] PREEMPT SMP
> > [ 1885.043131] Modules linked in:
> > [ 1885.043200] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W       4.12.0-rc5-00039-gf1d4a187881e #34
> > [ 1885.043299] Hardware name: FVP_Base_AEMv8A-AEMv8A (DT)
> > [ 1885.043364] task: ffff000008c21a80 task.stack: ffff000008c10000
> > [ 1885.043436] PC is at __memset+0x1ac/0x1d0
> > [ 1885.043499] LR is at __arm_spe_pmu_next_off+0x6c/0xd8
> > [ 1885.043600] pc : [<ffff00000837dbac>] lr : [<ffff0000086771e4>] pstate: 204001c9
> > [ 1885.043600] sp : ffff80007df22d10
> > [ 1885.043733] x29: ffff80007df22d10 x28: ffff000008c21a80 
> > [ 1885.043819] x27: ffff000008c37768 x26: ffff80007df30280 
> > [ 1885.043910] x25: ffff80007a109800 x24: 0000001d507d1906 
> > [ 1885.044012] x23: ffff80007a601018 x22: ffff80007a3ebb00 
> > [ 1885.044102] x21: ffff80007df36ab0 x20: ffff80007a3ebb00 
> > [ 1885.044196] x19: ffff80007df36ab0 x18: 0000000000000000 
> > [ 1885.044253] x17: 0000000000000000 x16: 0000000000000000 
> > [ 1885.044339] x15: 0000000000000000 x14: ffff000008c21a80 
> > [ 1885.044456] x13: 000080007532d000 x12: 000000003445d91d 
> > [ 1885.044557] x11: 0000000000000000 x10: 0000000000001000 
> > [ 1885.044600] x9 : 0000000000000000 x8 : ffff00000adac000 
> > [ 1885.044729] x7 : 0000000000000000 x6 : 00000000000003ff 
> > [ 1885.044800] x5 : 0000000000000400 x4 : 0000000000000000 
> > [ 1885.044911] x3 : 0000000000000008 x2 : 0000000000003bff 
> > [ 1885.045000] x1 : 0000000000000000 x0 : ffff00000ada8000 
> > [ 1885.045100] Process swapper/0 (pid: 0, stack limit = 0xffff000008c10000)
> > [ 1885.045179] Stack: (0xffff80007df22d10 to 0xffff000008c14000)
> > [ 1885.045239] Call trace:
> 
> > [ 1885.046408] [<ffff00000837dbac>] __memset+0x1ac/0x1d0
> > [ 1885.046499] [<ffff00000867729c>] arm_spe_perf_aux_output_begin+0x4c/0x1b8
> > [ 1885.046599] [<ffff000008678424>] arm_spe_pmu_start+0x34/0xf0
> > [ 1885.046695] [<ffff000008678548>] arm_spe_pmu_add+0x68/0x98
> > [ 1885.046733] [<ffff00000814da54>] event_sched_in.isra.61+0xcc/0x218
> > [ 1885.046879] [<ffff00000814dc08>] group_sched_in+0x68/0x1a0
> > [ 1885.046981] [<ffff00000814dfd0>] ctx_sched_in+0x290/0x468
> > [ 1885.047080] [<ffff00000814e23c>] perf_event_sched_in+0x94/0xa8
> > [ 1885.047179] [<ffff00000814e2b4>] ctx_resched+0x64/0xb0
> > [ 1885.047268] [<ffff00000814e500>] __perf_event_enable+0x200/0x238
> > [ 1885.047366] [<ffff000008147118>] event_function+0x90/0xf0
> > [ 1885.047452] [<ffff0000081499e8>] remote_function+0x60/0x70
> > [ 1885.047514] [<ffff0000081194fc>] flush_smp_call_function_queue+0x9c/0x168
> > [ 1885.047637] [<ffff00000811a2a0>] generic_smp_call_function_single_interrupt+0x10/0x18
> > [ 1885.047733] [<ffff00000808e928>] handle_IPI+0xc0/0x1d8
> > [ 1885.047799] [<ffff000008081700>] gic_handle_irq+0x80/0x178
> 
> > [ 1885.048900] [<ffff0000080827f4>] el1_irq+0xb4/0x128
> > [ 1885.049009] [<ffff00000861018c>] cpuidle_enter_state+0x154/0x200
> > [ 1885.049126] [<ffff000008610270>] cpuidle_enter+0x18/0x20
> > [ 1885.049207] [<ffff0000080ddd08>] call_cpuidle+0x18/0x30
> > [ 1885.049332] [<ffff0000080ddf44>] do_idle+0x19c/0x1d8
> > [ 1885.049400] [<ffff0000080de114>] cpu_startup_entry+0x24/0x28
> > [ 1885.049453] [<ffff0000087a6b30>] rest_init+0x80/0x90
> > [ 1885.049500] [<ffff000008b10b3c>] start_kernel+0x374/0x388
> > [ 1885.049617] [<ffff000008b101e0>] __primary_switched+0x64/0x6c
> > [ 1885.049699] Code: 91010108 54ffff4a 8b040108 cb050042 (d50b7428) 
> > [ 1885.049800] ---[ end trace 31b9a9f27da95f58 ]---
> > [ 1885.049900] Kernel panic - not syncing: Fatal exception in interrupt
> > [ 1885.050000] SMP: stopping secondary CPUs
> > [ 1885.050204] Kernel Offset: disabled
> > [ 1885.050240] Memory Limit: none
> > [ 1885.050327] ---[ end Kernel panic - not syncing: Fatal exception in interrupt
> 
> That's worrying. I'll see if I can reproduce this.

Actually, this might be down to the IDX2OFF() macro being borked for non
power-of-two buffer sizes.

Do you have Will's latest fixes? In his tree there's a commit:

  4f331cd62531dce2 ("squash! drivers/perf: Add support for ARMv8.2 Statistical Profiling Extension")

... which should fix the IDX2OFF() bug.

It's be good to reproduce the issue if we can, regardless.

Thanks,
Mark.