Fwd: [Bug 213069] New: kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:147! Oops: Exception in kernel mode, sig: 5 [#1]

[Christophe Leroy]

+aneesh
+linuxppc-dev list

Le 17/05/2021 à 07:44, Anshuman Khandual a écrit :
> Hello Christophe,
> 
> DEBUG_VM_PGTABLE has now been re-enabled on powerpc recently ? was not
> aware about this. From the error log, it failed explicitly on 4K page
> size hash config.
> 
> static inline pmd_t hash__pmd_mkhuge(pmd_t pmd)
> {
>          BUG();		------> Failed
>          return pmd;
> }
> 
> static inline pmd_t __pmd_mkhuge(pmd_t pmd)
> {
>          if (radix_enabled())
>                  return radix__pmd_mkhuge(pmd);
>          return hash__pmd_mkhuge(pmd);
> }
> 
> pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
> {
>          unsigned long pmdv;
> 
>          pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
> 
>          return __pmd_mkhuge(pmd_set_protbits(__pmd(pmdv), pgprot));
> }
> 
> It seems like on powerpc, where pfn_pmd() makes a huge page but which
> is not supported on 4K hash config thus triggering the BUG(). But all
> pfn_pmd() call sites inside the debug_vm_pgtable() test are protected
> with CONFIG_TRANSPARENT_HUGEPAGE. IIUC unlike powerpc, pfn_pmd() does
> not directly make a huge page on other platforms.
> 
> Looking at arch/powerpc/include/asm/book3s/64/hash-4k.h, all relevant
> THP helpers has BUG() or 0 which indicates THP might not be supported
> on 4K page size hash config ?
> 
> But looking at arch/powerpc/platforms/Kconfig.cputype, it seems like
> HAVE_ARCH_TRANSPARENT_HUGEPAGE is invariably selected on PPC_BOOK3S_64
> platforms which I assume includes 4K page size hash config as well.
> 
> Is THP some how getting enabled on this 4K page size hash config where
> it should not be (thus triggering the BUG) ? OR am I missing something
> here.
> 
> - Anshuman
> 
> On 5/15/21 7:52 PM, Christophe Leroy wrote:
>> ------------[ cut here ]------------
>> kernel BUG at arch/powerpc/include/asm/book3s/64/hash-4k.h:147!
>> Oops: Exception in kernel mode, sig: 5 [#1]
>> BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=4 NUMA PowerMac
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W         5.13.0-rc1-PowerMacG5
>> #2
>> NIP:  c00000000003d6fc LR: c000000001024bc8 CTR: c0000000000f778c
>> REGS: c0000000025f7840 TRAP: 0700   Tainted: G        W
>> (5.13.0-rc1-PowerMacG5)
>> MSR:  9000000000029032 <SF,HV,EE,ME,IR,DR,RI>  CR: 44002448  XER: 00000000
>> IRQMASK: 0
>> GPR00: c000000001024a5c c0000000025f7ae0 c00000000129f800 c0000000025f7b58
>> GPR04: 0000000000001000 8000000000000108 0000000000000000 0000000000000001
>> GPR08: 0000000000000000 0000000000000000 0000000000000008 0000000000000200
>> GPR12: 0000000024002440 c000000002366000 c00000000001003c 0000000000000000
>> GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>> GPR20: c0000000011b3388 c000000000b013e8 c0000000011b3108 4000000000000006
>> GPR24: 4000000000000280 00000000011b3000 0000000000000000 8000000000000105
>> GPR28: 0000000000001000 ffffffffffffff7f c000000000b01460 80000000011b3108
>> NIP [c00000000003d6fc] .pfn_pmd+x0x/0x4
>> LR [c000000001024bc8] .debug_vm_pgtable+0x3f4/0x51c
>> Call Trace:
>> [c0000000025f7ae0] [c000000001024a5c] .debug_vm_pgtable+0x288/0x51c
>> (unreliable)
>> [c0000000025f7bd0] [c00000000000fa58] .do_one_initcall+0x104/0x2c4
>> [c0000000025f7cb0] [c000000001003dec] .kernel_init_freeable+0x3d4/0x410
>> [c0000000025f7da0] [c00000000001004c] .kernel_init+0x10/0x15c
>> [c0000000025f7e10] [c00000000000bbf4] .ret_from_kernel_thread+0x58/0x64
>> Instruction dump:
>> 4bffcd05 60000000 e9210078 e94d0370 7d295279 39400000 4182000c 487d3829
>> 60000000 38210090 7fe3fb78 487dacf4 <0fe00000> 7c0802a6 f8010010 f821ff71
>> ---[ end trace 21fc0fb84dac9a9b ]---