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SubjectRe: [PATCH v5 05/10] powerpc/smp: Dont assume l2-cache to be superset of sibling
Date
Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> * Michael Ellerman <mpe@ellerman.id.au> [2020-09-11 21:55:23]:
>
>> Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
>> > Current code assumes that cpumask of cpus sharing a l2-cache mask will
>> > always be a superset of cpu_sibling_mask.
>> >
>> > Lets stop that assumption. cpu_l2_cache_mask is a superset of
>> > cpu_sibling_mask if and only if shared_caches is set.
>>
>> I'm seeing oopses with this:
>>
>> [ 0.117392][ T1] smp: Bringing up secondary CPUs ...
>> [ 0.156515][ T1] smp: Brought up 2 nodes, 2 CPUs
>> [ 0.158265][ T1] numa: Node 0 CPUs: 0
>> [ 0.158520][ T1] numa: Node 1 CPUs: 1
>> [ 0.167453][ T1] BUG: Unable to handle kernel data access on read at 0x8000000041228298
>> [ 0.167992][ T1] Faulting instruction address: 0xc00000000018c128
>> [ 0.168817][ T1] Oops: Kernel access of bad area, sig: 11 [#1]
>> [ 0.168964][ T1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
>> [ 0.169417][ T1] Modules linked in:
>> [ 0.170047][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc2-00095-g7430ad5aa700 #209
>> [ 0.170305][ T1] NIP: c00000000018c128 LR: c00000000018c0cc CTR: c00000000004dce0
>> [ 0.170498][ T1] REGS: c00000007e343880 TRAP: 0380 Not tainted (5.9.0-rc2-00095-g7430ad5aa700)
>> [ 0.170602][ T1] MSR: 8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE> CR: 44002222 XER: 00000000
>> [ 0.170985][ T1] CFAR: c00000000018c288 IRQMASK: 0
>> [ 0.170985][ T1] GPR00: 0000000000000000 c00000007e343b10 c00000000173e400 0000000000004000
>> [ 0.170985][ T1] GPR04: 0000000000000000 0000000000000800 0000000000000800 0000000000000000
>> [ 0.170985][ T1] GPR08: 0000000000000000 c00000000122c298 c00000003fffc000 c00000007fd05ce8
>> [ 0.170985][ T1] GPR12: c00000007e0119f8 c000000001930000 00000000ffff8ade 0000000000000000
>> [ 0.170985][ T1] GPR16: c00000007e3c0640 0000000000000917 c00000007e3c0658 0000000000000008
>> [ 0.170985][ T1] GPR20: c0000000015d0bb8 00000000ffff8ade c000000000f57400 c000000001817c28
>> [ 0.170985][ T1] GPR24: c00000000176dc80 c00000007e3c0890 c00000007e3cfe00 0000000000000000
>> [ 0.170985][ T1] GPR28: c000000001772310 c00000007e011900 c00000007e3c0800 0000000000000001
>> [ 0.172750][ T1] NIP [c00000000018c128] build_sched_domains+0x808/0x14b0
>> [ 0.172900][ T1] LR [c00000000018c0cc] build_sched_domains+0x7ac/0x14b0
>> [ 0.173186][ T1] Call Trace:
>> [ 0.173484][ T1] [c00000007e343b10] [c00000000018bfe8] build_sched_domains+0x6c8/0x14b0 (unreliable)
>> [ 0.173821][ T1] [c00000007e343c50] [c00000000018dcdc] sched_init_domains+0xec/0x130
>> [ 0.174037][ T1] [c00000007e343ca0] [c0000000010d59d8] sched_init_smp+0x50/0xc4
>> [ 0.174207][ T1] [c00000007e343cd0] [c0000000010b45c4] kernel_init_freeable+0x1b4/0x378
>> [ 0.174378][ T1] [c00000007e343db0] [c0000000000129fc] kernel_init+0x24/0x158
>> [ 0.174740][ T1] [c00000007e343e20] [c00000000000d9d0] ret_from_kernel_thread+0x5c/0x6c
>> [ 0.175050][ T1] Instruction dump:
>> [ 0.175626][ T1] 554905ee 71480040 7d2907b4 4182016c 2c290000 3920006e 913e002c 41820034
>> [ 0.175841][ T1] 7c6307b4 e9300020 78631f24 7d58182a <7d2a482a> f93e0080 7d404828 314a0001
>> [ 0.178340][ T1] ---[ end trace 6876b88dd1d4b3bb ]---
>> [ 0.178512][ T1]
>> [ 1.180458][ T1] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>>
>> That's qemu:
>>
>> qemu-system-ppc64 -nographic -vga none -M pseries -cpu POWER8 \
>> -kernel build~/vmlinux \
>> -m 2G,slots=2,maxmem=4G \
>> -object memory-backend-ram,size=1G,id=m0 \
>> -object memory-backend-ram,size=1G,id=m1 \
>> -numa node,nodeid=0,memdev=m0 \
>> -numa node,nodeid=1,memdev=m1 \
>> -smp 2,sockets=2,maxcpus=2 \
>>
>
> Thanks Michael for the report and also for identifying the patch and also
> giving an easy reproducer. That made my task easy. (My only problem was all
> my PowerKVM hosts had a old compiler that refuse to compile never kernels.)
>
> So in this setup, CPU doesn't have a l2-cache. And in that scenario, we
> miss updating the l2-cache domain. Actually the initial patch had this
> exact code. However it was my mistake. I should have reassessed it before
> making changes suggested by Gautham.
>
> Patch below. Do let me know if you want me to send the patch separately.

>> On mambo I get:
>>
>> [ 0.005069][ T1] smp: Bringing up secondary CPUs ...
>> [ 0.011656][ T1] smp: Brought up 2 nodes, 8 CPUs
>> [ 0.011682][ T1] numa: Node 0 CPUs: 0-3
>> [ 0.011709][ T1] numa: Node 1 CPUs: 4-7
>> [ 0.012015][ T1] BUG: arch topology borken
>> [ 0.012040][ T1] the SMT domain not a subset of the CACHE domain
>> [ 0.012107][ T1] BUG: Unable to handle kernel data access on read at 0x80000001012e7398
>> [ 0.012142][ T1] Faulting instruction address: 0xc0000000001aa4f0
>> [ 0.012174][ T1] Oops: Kernel access of bad area, sig: 11 [#1]
>> [ 0.012206][ T1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA PowerNV
>> [ 0.012236][ T1] Modules linked in:
>> [ 0.012264][ T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc2-00095-g7430ad5aa700 #1
>> [ 0.012304][ T1] NIP: c0000000001aa4f0 LR: c0000000001aa498 CTR: 0000000000000000
>> [ 0.012341][ T1] REGS: c0000000ef583880 TRAP: 0380 Not tainted (5.9.0-rc2-00095-g7430ad5aa700)
>> [ 0.012379][ T1] MSR: 9000000002009033 <SF,HV,VEC,EE,ME,IR,DR,RI,LE> CR: 44002222 XER: 00040000
>> [ 0.012439][ T1] CFAR: c0000000000101b0 IRQMASK: 0
>> [ 0.012439][ T1] GPR00: 0000000000000000 c0000000ef583b10 c0000000017fd000 0000000000004000
>> [ 0.012439][ T1] GPR04: 0000000000000000 0000000000000800 0000000000000000 0000000000000000
>> [ 0.012439][ T1] GPR08: 0000000000000000 c0000000012eb398 c0000000ffffc000 0000000000000000
>> [ 0.012439][ T1] GPR12: 0000000000000020 c0000000019f0000 00000000ffff8ad1 0000000000000000
>> [ 0.012439][ T1] GPR16: c0000000ef068658 c0000000018d7ba8 0000000000000008 c000000001690bb8
>> [ 0.012439][ T1] GPR20: c00000000182dc80 c0000000ef06be90 00000000ffff8ad1 c000000001014aa8
>> [ 0.012439][ T1] GPR24: 0000000000000917 c0000000ef068e00 0000000000000000 c0000000ef06be00
>> [ 0.012439][ T1] GPR28: 0000000000000001 c0000000ef068640 c0000000ef4a1800 c000000001832310
>> [ 0.012774][ T1] NIP [c0000000001aa4f0] build_sched_domains+0x5c0/0x14f0
>> [ 0.012812][ T1] LR [c0000000001aa498] build_sched_domains+0x568/0x14f0
>> [ 0.012842][ T1] Call Trace:
>> [ 0.012872][ T1] [c0000000ef583b10] [c0000000001aa3b4] build_sched_domains+0x484/0x14f0 (unreliable)
>> [ 0.012922][ T1] [c0000000ef583c50] [c0000000001ac3d8] sched_init_domains+0xd8/0x120
>> [ 0.012966][ T1] [c0000000ef583ca0] [c0000000011962d0] sched_init_smp+0x50/0xc4
>> [ 0.013008][ T1] [c0000000ef583cd0] [c00000000117451c] kernel_init_freeable+0x1b4/0x378
>> [ 0.013051][ T1] [c0000000ef583db0] [c000000000012994] kernel_init+0x2c/0x158
>> [ 0.013092][ T1] [c0000000ef583e20] [c00000000000d9d0] ret_from_kernel_thread+0x5c/0x6c
>> [ 0.013128][ T1] Instruction dump:
>> [ 0.013151][ T1] e93b003a 712a0040 552a05ee 418203c4 2c2a0000 3920006e 913b002c 41820034
>> [ 0.013206][ T1] 7c6307b4 e93d0020 78631f24 7d54182a <7d2a482a> f93b0080 7d404828 314a0001
>> [ 0.013267][ T1] ---[ end trace 1bf5f6f38a9fd096 ]---
>>
>
> I haven't tried Mambo. But the problem report looks similar.

The patch fixes qemu, and I don't see the crash on mambo, but I still
see:

[ 0.010536] smp: Bringing up secondary CPUs ...
[ 0.019189] smp: Brought up 2 nodes, 8 CPUs
[ 0.019210] numa: Node 0 CPUs: 0-3
[ 0.019235] numa: Node 1 CPUs: 4-7
[ 0.023669] BUG: arch topology borken
[ 0.023690] the SMT domain not a subset of the CACHE domain
[ 0.023726] BUG: arch topology borken
[ 0.023747] the CACHE domain not a subset of the MC domain
[ 0.023808] BUG: arch topology borken
[ 0.023829] the SMT domain not a subset of the CACHE domain
[ 0.023865] BUG: arch topology borken
[ 0.023887] the CACHE domain not a subset of the MC domain
[ 0.023948] BUG: arch topology borken
[ 0.023969] the SMT domain not a subset of the CACHE domain
[ 0.024005] BUG: arch topology borken
[ 0.024026] the CACHE domain not a subset of the MC domain
[ 0.024087] BUG: arch topology borken
[ 0.024108] the SMT domain not a subset of the CACHE domain
[ 0.024144] BUG: arch topology borken
[ 0.024165] the CACHE domain not a subset of the MC domain
[ 0.024227] BUG: arch topology borken
[ 0.024248] the SMT domain not a subset of the CACHE domain
[ 0.024284] BUG: arch topology borken
[ 0.024305] the CACHE domain not a subset of the MC domain
[ 0.024366] BUG: arch topology borken
[ 0.024387] the SMT domain not a subset of the CACHE domain
[ 0.024423] BUG: arch topology borken
[ 0.024444] the CACHE domain not a subset of the MC domain
[ 0.024505] BUG: arch topology borken
[ 0.024527] the SMT domain not a subset of the CACHE domain
[ 0.024563] BUG: arch topology borken
[ 0.024584] the CACHE domain not a subset of the MC domain
[ 0.024645] BUG: arch topology borken
[ 0.024666] the SMT domain not a subset of the CACHE domain
[ 0.024702] BUG: arch topology borken
[ 0.024723] the CACHE domain not a subset of the MC domain

That's the p9 mambo model, using skiboot.tcl from skiboot, with CPUS=2,
THREADS=4 and MAMBO_NUMA=1.

Node layout is:

[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000000000000-0x00000000ffffffff]
[ 0.000000] node 1: [mem 0x0000200000000000-0x00002000ffffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x00000000ffffffff]
[ 0.000000] On node 0 totalpages: 65536
[ 0.000000] Initmem setup node 1 [mem 0x0000200000000000-0x00002000ffffffff]
[ 0.000000] On node 1 totalpages: 65536


There aren't any l2-cache properties in the device-tree under cpus.

I'll try and have a closer look tonight.

cheers

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