Re: [PATCH 1/4] x86/percpu: Use explicit segment registers in lib/cmpxchg{8,16}b_emu.S

[Uros Bizjak <ubizjak@xxxxxxxxx>]

On Thu, Oct 26, 2023 at 9:01 AM kernel test robot <oliver.sang@xxxxxxxxx> wrote:
>
>
>
> Hello,
>
> kernel test robot noticed "general_protection_fault:#[##]" on:
>
> commit: 33c7952d925e905f7af1fb7628e48e03f59885da ("[PATCH 1/4] x86/percpu: 
> Use explicit segment registers in lib/cmpxchg{8,16}b_emu.S")
> url: 
> https://github.com/intel-lab-lkp/linux/commits/Uros-Bizjak/x86-percpu-Use-explicit-segment-registers-in-lib-cmpxchg-8-16-b_emu-S/20231017-111304
> base: https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git 
> 92fe9bb77b0c9fade150350fdb0629a662f0923f
> patch link: 
> https://lore.kernel.org/all/20231012161237.114733-2-ubizjak@xxxxxxxxx/
> patch subject: [PATCH 1/4] x86/percpu: Use explicit segment registers in 
> lib/cmpxchg{8,16}b_emu.S
>
> in testcase: boot
>
> compiler: gcc-12
> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G

This problem was fixed in a -v3 version of the patch [1], that was
committed to the tip/percpu branch and later merged into tip/master.

[1] https://lore.kernel.org/lkml/20231017162811.200569-3-ubizjak@xxxxxxxxx/

Thanks,
Uros.

>
> (please refer to attached dmesg/kmsg for entire log/backtrace)
>
>
> +------------------------------------------+------------+------------+
> |                                          | 92fe9bb77b | 33c7952d92 |
> +------------------------------------------+------------+------------+
> | boot_successes                           | 7          | 0          |
> | boot_failures                            | 0          | 7          |
> | general_protection_fault:#[##]           | 0          | 7          |
> | EIP:this_cpu_cmpxchg8b_emu               | 0          | 7          |
> | Kernel_panic-not_syncing:Fatal_exception | 0          | 7          |
> +------------------------------------------+------------+------------+
>
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version 
> of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> | Closes: 
> https://lore.kernel.org/oe-lkp/202310261417.b269d37e-oliver.sang@xxxxxxxxx
>
>
> [    0.186570][    T0] stackdepot hash table entries: 65536 (order: 6, 262144 
> bytes, linear)
> [    0.187499][    T0] Initializing HighMem for node 0 (0002ebfe:000bffe0)
> [    1.727965][    T0] Initializing Movable for node 0 (00000000:00000000)
> [    1.943274][    T0] Checking if this processor honours the WP bit even in 
> supervisor mode...Ok.
> [    1.944313][    T0] Memory: 2896220K/3145208K available (16182K kernel 
> code, 5537K rwdata, 11756K rodata, 816K init, 9720K bss, 248988K reserved, 0K 
> cma-reserved, 2379656K highmem)
> [    1.947172][    T0] general protection fault: 0000 [#1] PREEMPT
> [    1.947900][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 
> 6.6.0-rc1-00024-g33c7952d925e #1 8d4b014f9a0a85cc9a3f6a52ed8e88f1e431f74e
> [    1.949317][    T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), 
> BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> [ 1.950480][ T0] EIP: this_cpu_cmpxchg8b_emu 
> (kbuild/src/consumer/arch/x86/lib/cmpxchg8b_emu.S:73)
> [ 1.951093][ T0] Code: ff ff ff 8d b4 26 00 00 00 00 66 90 83 c6 01 3c 3d 0f 
> 95 c0 0f b6 c0 83 c0 01 e9 56 ff ff ff bf ff ff ff ff eb a6 cc cc 9c fa <64> 
> 3b 06 75 13 64 3b 56 04 75 0d 64 89 1e 64 89 4e 04 83 0c 24 40
> All code
> ========
>    0:   ff                      (bad)
>    1:   ff                      (bad)
>    2:   ff 8d b4 26 00 00       decl   0x26b4(%rbp)
>    8:   00 00                   add    %al,(%rax)
>    a:   66 90                   xchg   %ax,%ax
>    c:   83 c6 01                add    $0x1,%esi
>    f:   3c 3d                   cmp    $0x3d,%al
>   11:   0f 95 c0                setne  %al
>   14:   0f b6 c0                movzbl %al,%eax
>   17:   83 c0 01                add    $0x1,%eax
>   1a:   e9 56 ff ff ff          jmp    0xffffffffffffff75
>   1f:   bf ff ff ff ff          mov    $0xffffffff,%edi
>   24:   eb a6                   jmp    0xffffffffffffffcc
>   26:   cc                      int3
>   27:   cc                      int3
>   28:   9c                      pushf
>   29:   fa                      cli
>   2a:*  64 3b 06                cmp    %fs:(%rsi),%eax          <-- trapping 
> instruction
>   2d:   75 13                   jne    0x42
>   2f:   64 3b 56 04             cmp    %fs:0x4(%rsi),%edx
>   33:   75 0d                   jne    0x42
>   35:   64 89 1e                mov    %ebx,%fs:(%rsi)
>   38:   64 89 4e 04             mov    %ecx,%fs:0x4(%rsi)
>   3c:   83 0c 24 40             orl    $0x40,(%rsp)
>
> Code starting with the faulting instruction
> ===========================================
>    0:   64 3b 06                cmp    %fs:(%rsi),%eax
>    3:   75 13                   jne    0x18
>    5:   64 3b 56 04             cmp    %fs:0x4(%rsi),%edx
>    9:   75 0d                   jne    0x18
>    b:   64 89 1e                mov    %ebx,%fs:(%rsi)
>    e:   64 89 4e 04             mov    %ecx,%fs:0x4(%rsi)
>   12:   83 0c 24 40             orl    $0x40,(%rsp)
> [    1.953397][    T0] EAX: c3c01100 EBX: c3c01180 ECX: 00000004 EDX: 00000003
> [    1.954231][    T0] ESI: e52cd090 EDI: e52cd090 EBP: c2b4bf00 ESP: c2b4bec4
> [    1.955060][    T0] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 
> 00210082
> [    1.955949][    T0] CR0: 80050033 CR2: ffdeb000 CR3: 031b5000 CR4: 00000090
> [    1.956783][    T0] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> [    1.957641][    T0] DR6: fffe0ff0 DR7: 00000400
> [    1.958190][    T0] Call Trace:
> [ 1.958554][ T0] ? show_regs 
> (kbuild/src/consumer/arch/x86/kernel/dumpstack.c:479)
> [ 1.959026][ T0] ? die_addr 
> (kbuild/src/consumer/arch/x86/kernel/dumpstack.c:421 
> kbuild/src/consumer/arch/x86/kernel/dumpstack.c:460)
> [ 1.959480][ T0] ? exc_general_protection 
> (kbuild/src/consumer/arch/x86/kernel/traps.c:697 
> kbuild/src/consumer/arch/x86/kernel/traps.c:642)
> [ 1.960101][ T0] ? exc_bounds 
> (kbuild/src/consumer/arch/x86/kernel/traps.c:642)
> [ 1.960579][ T0] ? handle_exception 
> (kbuild/src/consumer/arch/x86/entry/entry_32.S:1049)
>
>
> The kernel config and materials to reproduce are available at:
> https://download.01.org/0day-ci/archive/20231026/202310261417.b269d37e-oliver.sang@xxxxxxxxx
>
>
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki
>