Re: PPC476 hangs during tlb flush after calling /init in crash kernel with linux 5.4+

[Eddie James]

On Wed, 2021-04-28 at 08:08 +0200, Christophe Leroy wrote:
> 
> Le 28/04/2021 à 00:42, Eddie James a écrit :
> > On Tue, 2021-04-27 at 19:26 +0200, Christophe Leroy wrote:
> > > Hi Eddies,
> > > 
> > > Le 27/04/2021 à 19:03, Eddie James a écrit :
> > > > Hi all,
> > > > 
> > > > I'm having a problem in simulation and hardware where my PPC476
> > > > processor stops executing instructions after callling /init. In
> > > > my
> > > > case
> > > > this is a bash script. The code descends to flush the TLB, and
> > > > somewhere in the loop in _tlbil_pid, the PC goes to
> > > > InstructionTLBError47x but does not go any further. This only
> > > > occurs in
> > > > the crash kernel environment, which is using the same kernel,
> > > > initramfs, and init script as the main kernel, which executed
> > > > fine.
> > > > I
> > > > do not see this problem with linux 4.19 or 3.10. I do see it
> > > > with
> > > > 5.4
> > > > and 5.10. I see a fair amount of refactoring in the PPC memory
> > > > management area between 4.19 and 5.4. Can anyone point me in a
> > > > direction to debug this further? My stack trace is below as I
> > > > can
> > > > run
> > > > gdb in simulation.
> > > 
> > > Can you bisect to pin point the culprit commit ?
> > 
> > Hi, thanks for your prompt reply.
> > 
> > Good idea! I have bisected to:
> > 
> > commit 9e849f231c3c72d4c3c1b07c9cd19ae789da0420 (b8-bad,
> > refs/bisect/bad)
> > Author: Christophe Leroy <christophe.leroy@xxxxxx>
> > Date:   Thu Feb 21 19:08:40 2019 +0000
> > 
> >      powerpc/mm/32s: use generic mmu_mapin_ram() for all blocks.
> >      
> >      Now that mmu_mapin_ram() is able to handle other blocks
> >      than the one starting at 0, the WII can use it for all
> >      its blocks.
> >      
> >      Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> >      Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> > 
> > I also confirmed that reverting this commit resolves the issue in
> > 5.4+.
> > 
> > Now, I don't understand why this is problematic or what is really
> > happening... Reverting is probably not the desired solution.
> > 
> 
> Can you provide the 'dmesg' or a dump of the logs printed by the
> kernel at boottime ?

Yes:

[    0.000000] Linux version 5.4.85-a19ab63.ppcnf-fsp2 (oe-user@oe-host
) (gcc ve
rsion 8.3.0 (GCC)) #1 Tue Mar 30 15:32:31 UTC 2021
[    0.000000] Found initrd at 0xcf6a7000:0xcfffb09f
[    0.000000] Using FSP-2 machine description
[    0.000000] Found legacy serial port 0 for /plb4/opb/serial@b0020000
[    0.000000]   mem=10b0020000, taddr=10b0020000, irq=0, clk=20833333,
speed=11
5200
[    0.000000] -----------------------------------------------------
[    0.000000] phys_mem_size     = 0x4000000
[    0.000000] dcache_bsize      = 0x80
[    0.000000] icache_bsize      = 0x20
[    0.000000] cpu_features      = 0x0000000040800120
[    0.000000]   possible        = 0x0000000040800120
[    0.000000]   always          = 0x0000000000000020
[    0.000000] cpu_user_features = 0x8c008000 0x00000000
[    0.000000] mmu_features      = 0x00140020
[    0.000000] physical_start    = 0xc000000
[    0.000000] -----------------------------------------------------
[    0.000000] Top of RAM: 0x10000000, Total RAM: 0x4000000
[    0.000000] Memory hole size: 192MB
[    0.000000] Zone ranges:
[    0.000000]   Normal   [mem 0x000000000c000000-0x000000000fffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x000000000c000000-0x000000000fffffff]
[    0.000000] Initmem setup node 0 [mem 0x000000000c000000-
0x000000000fffffff]
[    0.000000] On node 0 totalpages: 16384
[    0.000000]   Normal zone: 160 pages used for memmap
[    0.000000]   Normal zone: 0 pages reserved
[    0.000000]   Normal zone: 16384 pages, LIFO batch:3
[    0.000000] MMU: Allocated 278528 bytes of context maps for 65535
contexts
[    0.000000] pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
[    0.000000] pcpu-alloc: [0] 0 
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages:
16224
[    0.000000] Kernel command line: console=ttyS0,115200 loglevel=9
rootwait roo
t=/dev/mmcblk0p2 elfcorehdr=209456K maxcpus=1
[    0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768
bytes, lin
ear)
[    0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384
bytes, line
ar)
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] Memory: 42028K/65536K available (7136K kernel code, 620K
rwdata, 
1916K rodata, 2080K init, 233K bss, 23508K reserved, 0K cma-reserved)
[    0.000000] Kernel virtual memory layout:
[    0.000000]   * 0xfffdf000..0xfffff000  : fixmap
[    0.000000]   * 0xd1000000..0xfffdf000  : vmalloc & ioremap
[    0.000000] SLUB: HWalign=128, Order=0-3, MinObjects=0, CPUs=1,
Nodes=1
[    0.000000] NR_IRQS: 512, nr_irqs: 512, preallocated irqs: 16
[    0.000000] UIC0 (32 IRQ sources) at DCR 0x2c0
[    0.000000] UIC1 (32 IRQ sources) at DCR 0x2c8
[    0.000000] UIC2 (32 IRQ sources) at DCR 0x350
[    0.000000] UIC3 (32 IRQ sources) at DCR 0x358
[    0.000000] UIC4 (32 IRQ sources) at DCR 0x360
[    0.000000] UIC5 (32 IRQ sources) at DCR 0x368
[    0.000000] UIC6 (32 IRQ sources) at DCR 0x370
[    0.000000] UIC7 (32 IRQ sources) at DCR 0x2d0
[    0.000000] UIC8 (32 IRQ sources) at DCR 0x2d8
[    0.000000] UIC17 (32 IRQ sources) at DCR 0x320
[    0.000000] UIC18 (32 IRQ sources) at DCR 0x328
[    0.000000] UIC19 (32 IRQ sources) at DCR 0x330
[    0.000000] UIC20 (32 IRQ sources) at DCR 0x338
[    0.000000] UIC21 (32 IRQ sources) at DCR 0x340
[    0.000000] UIC22 (32 IRQ sources) at DCR 0x348
[    0.000000] UIC9 (32 IRQ sources) at DCR 0x2e0
[    0.000000] UIC10 (32 IRQ sources) at DCR 0x2e8
[    0.000000] UIC11 (32 IRQ sources) at DCR 0x2f0
[    0.000000] UIC12 (32 IRQ sources) at DCR 0x2f8
[    0.000000] UIC13 (32 IRQ sources) at DCR 0x300
[    0.000000] UIC14 (32 IRQ sources) at DCR 0x308
[    0.000000] UIC15 (32 IRQ sources) at DCR 0x310
[    0.000000] UIC16 (32 IRQ sources) at DCR 0x318
[    0.000000] random: get_random_u32 called from
start_kernel+0x32c/0x500 with 
crng_init=0
[    0.000000] time_init: decrementer frequency = 166.666667 MHz
[    0.000000] time_init: processor frequency   = 1333.333333 MHz
[    0.000004] clocksource: timebase: mask: 0xffffffffffffffff
max_cycles: 0x267
03d839d, max_idle_ns: 440795207088 ns
[    0.000007] clocksource: timebase mult[6000000] shift[24] registered
[    0.000011] clockevent: decrementer mult[2aaaaaac] shift[32] cpu[0]
[    0.000071] pid_max: default: 32768 minimum: 301
[    0.000107] Mount-cache hash table entries: 1024 (order: 0, 4096
bytes, linea
r)
[    0.000111] Mountpoint-cache hash table entries: 1024 (order: 0,
4096 bytes, 
linear)
[    0.000580] devtmpfs: initialized
[    0.002029] clocksource: jiffies: mask: 0xffffffff max_cycles:
0xffffffff, ma
x_idle_ns: 7645041785100000 ns
[    0.002034] futex hash table entries: 256 (order: -1, 3072 bytes,
linear)
[    0.002146] NET: Registered protocol family 16
[    0.004958] SCSI subsystem initialized
[    0.004973] libata version 3.00 loaded.
[    0.005003] usbcore: registered new interface driver usbfs
[    0.005019] usbcore: registered new interface driver hub
[    0.005031] usbcore: registered new device driver usb
[    0.005043] pps_core: LinuxPPS API ver. 1 registered
[    0.005045] pps_core: Software ver. 5.3.6 - Copyright 2005-2007
Rodolfo Giome
tti <giometti@xxxxxxxx>
[    0.005052] PTP clock support registered
[    0.005257] clocksource: Switched to clocksource timebase
[    0.311619] thermal_sys: Registered thermal governor 'step_wise'
[    0.311665] NET: Registered protocol family 2
[    0.311834] tcp_listen_portaddr_hash hash table entries: 512 (order:
0, 4096 
bytes, linear)
[    0.311844] TCP established hash table entries: 1024 (order: 0, 4096
bytes, l
inear)
[    0.311855] TCP bind hash table entries: 1024 (order: 0, 4096 bytes,
linear)
[    0.311864] TCP: Hash tables configured (established 1024 bind 1024)
[    0.311877] UDP hash table entries: 256 (order: 0, 4096 bytes,
linear)
[    0.311885] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes,
linear)
[    0.311918] NET: Registered protocol family 1
[    0.311994] RPC: Registered named UNIX socket transport module.
[    0.311996] RPC: Registered udp transport module.
[    0.311999] RPC: Registered tcp transport module.
[    0.312001] RPC: Registered tcp NFSv4.1 backchannel transport
module.
[    0.312043] Trying to unpack rootfs image as initramfs...
[    0.632637] Freeing initrd memory: 9552K
[    0.634361] shadow_disr_to_uic15: 0x00000020 to uic15_pr
[    0.635621] workingset: timestamp_bits=30 max_order=14
bucket_order=0
[    0.638710] NFS: Registering the id_resolver key type
[    0.638717] Key type id_resolver registered
[    0.638720] Key type id_legacy registered
[    0.638730] jffs2: version 2.2. (NAND) (SUMMARY)  © 2001-2006 Red
Hat, Inc.
[    0.638858] fuse: init (API version 7.31)
[    0.664372] io scheduler mq-deadline registered
[    0.664375] io scheduler kyber registered
[    0.664573] Serial: 8250/16550 driver, 32 ports, IRQ sharing enabled
[    0.665728] printk: console [ttyS0] disabled
[    0.685664] serial8250.0: ttyS0 at MMIO 0x10b0020000 (irq = 47,
base_baud = 1
302083) is a 16550A
[    0.693859] printk: console [ttyS0] enabled
[    0.694150] printk: console [ttyS0] disabled
[    0.694212] 10b0020000.serial: ttyS0 at MMIO 0x10b0020000 (irq = 47,
base_bau
d = 1302083) is a 16550
[    0.702632] printk: console [ttyS0] enabled
[    0.704642] brd: module loaded
[    0.704730] slram: not enough parameters.
[    0.704792] PPP generic driver version 2.4.2
[    0.704875] PPP Deflate Compression module registered
[    0.704941] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI)
Driver
[    0.705052] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[    0.705148] usbcore: registered new interface driver usb-storage
[    0.705248] usbcore: registered new interface driver
usbserial_generic
[    0.705341] usbserial: USB Serial support registered for generic
[    0.705428] usbcore: registered new interface driver pl2303
[    0.705508] usbserial: USB Serial support registered for pl2303
[    0.705592] booke_wdt: powerpc book-e watchdog driver loaded
[    0.705769] sdhci: Secure Digital Host Controller Interface driver
[    0.705849] sdhci: Copyright(c) Pierre Ossman
[    0.705906] sdhci-pltfm: SDHCI platform and OF driver helper
[    0.706033] mmc0: Invalid maximum block size, assuming 512 bytes
[    0.706112] mmc0 bounce up to 128 segments into one, max segment
size 65536 b
ytes
[    0.731266] mmc0: SDHCI controller on 10020c0000.emmc
[10020c0000.emmc] using
 DMA
[    0.731422] oprofile: using timer interrupt.
[    0.731546] Initializing XFRM netlink socket
[    0.731789] NET: Registered protocol family 10
[    0.732013] Segment Routing with IPv6
[    0.732096] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[    0.732331] NET: Registered protocol family 17
[    0.732414] sctp: Hash tables configured (bind 1024/1024)
[    0.732591] Key type dns_resolver registered
[    0.732698] drmem: No dynamic reconfiguration memory found
[    0.732888] hctosys: unable to open rtc device (rtc0)
[    0.734057] Freeing unused kernel memory: 2080K
[    0.734116] This architecture does not have kernel memory
protection.
[    0.734199] Run /init as init process

> 
> The difference with this commit is that if there are several
> memblocks, all get mapped. Maybe your 
> target doesn't like it.
> 
> You are talking about simulation, are you using QEMU ? If yes can you
> provide details so that I can 
> try and reproduce the issue ?

No, we use Windriver simics for this system. I'm not sure if QEMU has a
model for the PPC476... and I suspect it won't recreate with a more
generic 32 bit ppc machine, though I can try and find out.

Thanks,
Eddie

> 
> Thanks
> Christophe