[BUG/REGRESSION] Kernel 4.5-rc1 on Acube Sam460ex AMCC 460ex Power PC motherboards

[Dan Williams]

On Wed, Jan 27, 2016 at 2:18 AM, Julian Margetson <runaway at candw.ms> wrote:
> On 1/26/2016 9:43 PM, Dan Williams wrote:

> diff --git a/mm/memory.c b/mm/memory.c
> index 30991f83d0bf..c44e387130b2 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1521,6 +1521,8 @@ static int insert_pfn(struct vm_area_struct
> *vma, unsigned long addr,
>                entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
>        else
>                entry = pte_mkspecial(pfn_t_pte(pfn, prot));
> +       pr_info("%s: entry: %#llx pfn: %#lx\n", __func__,
> +                       (unsigned long long) entry, pfn_t_to_pfn(pfn));
>        set_pte_at(mm, addr, pte, entry);
>        update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
>
> ...of course for the passing case you'll need to drop the call to
> pfn_t_to_pfn() and just print the pfn directly.
>
> Thank you for the help tracking this down, it's much appreciated.
>
> Happy to help out. Just need some guidance sometimes as I am relatively new
> at this.

No worries.

So, below is the failing case, what does insert_pfn print in the
passing case?  No need for the full log just the first few lines after
starting X when running the commit before this failing one... (commit
69660fd797c3 "x86, mm: introduce _PAGE_DEVMAP").

I'm still stumped given that PTE_RPN_SHIFT==PAGE_SHIFT in this
configuration, so there's no 64-bit to 32-bit truncation to worry
about...

> -----------------------------------------------------------------------------------------------------------------------------
> 15.802615] systemd[1]: Started Journal Service.
> [   44.263074] Oops: Machine check, sig: 7 [#1]
> [   44.267603] PREEMPT Canyonlands
> [   44.270938] Modules linked in:
> [   44.274182] CPU: 0 PID: 586 Comm: Xorg Tainted: G        W
> 4.5.0-rc1-Sam460ex #2
> [   44.282538] task: ecd505c0 ti: efff2000 task.ti: ecd76000
> [   44.288239] NIP: c0000cec LR: 1fb81404 CTR: 1fb814d0
> [   44.293483] REGS: efff3f10 TRAP: 0214   Tainted: G        W
> (4.5.0-rc1-Sam460ex)
> [   44.301926] MSR: 00021000 <CE,ME>  CR: 84004242  XER: 00000000
> [   44.308185]
> GPR00: 1f045134 bfd0ce80 b7e7b6f0 b763dffc b6e54008 00000780 00000004
> 00000000
> GPR08: 00000000 b763dffc b6e54010 ecf50000 ecf50000 00000009 00000000
> 00000780
> GPR16: 00000000 00000020 00000000 00000000 00001e00 2079b638 00000438
> b6e54008
> GPR24: 00000780 bfd0ced8 20785770 b763e000 b763e000 b6e54008 1fc89ff4
> 00001e00
> [   44.340039] NIP [c0000cec] DataTLBError44x+0x6c/0x90
> [   44.345279] LR [1fb81404] 0x1fb81404
> [   44.349053] Call Trace:
> [   44.351631] Instruction dump:
> [   44.354776] 7d7342a6 816b0040 7d92eaa6 7db00aa6 51ac063e 7d92eba6
> 7d9e0aa6 39a00009
> [   44.363081] 518d57bc 554c6cfa 7d6c582e 556c0029 <4182003c> 514cbd38
> 816c0000 818c0004
> [   44.524699] ---[ end trace 439fa29153308785 ]---
> [   44.529322]
> [   47.216536] insert_pfn: entry: 0x80ed246b pfn: 0x80ed2
> [   47.221777] insert_pfn: entry: 0x80ed346b pfn: 0x80ed3
> [   47.228485] insert_pfn: entry: 0x80ed446b pfn: 0x80ed4
> [   47.237798] insert_pfn: entry: 0x80ed546b pfn: 0x80ed5
> [   47.249809] insert_pfn: entry: 0x80ed646b pfn: 0x80ed6
> [   47.257588] insert_pfn: entry: 0x80ed746b pfn: 0x80ed7
> [   47.265879] insert_pfn: entry: 0x80ed846b pfn: 0x80ed8
> [   47.275825] insert_pfn: entry: 0x80ed946b pfn: 0x80ed9
> [   47.281437] insert_pfn: entry: 0x80eda46b pfn: 0x80eda
> [   47.288113] insert_pfn: entry: 0x80edb46b pfn: 0x80edb
> [   47.293660] insert_pfn: entry: 0x80edc46b pfn: 0x80edc
> [   47.299834] insert_pfn: entry: 0x80edd46b pfn: 0x80edd
> [   47.305223] insert_pfn: entry: 0x80ede46b pfn: 0x80ede
> [   47.314891] insert_pfn: entry: 0x80edf46b pfn: 0x80edf
> [   47.329777] insert_pfn: entry: 0x80ee046b pfn: 0x80ee0
> [   47.339769] insert_pfn: entry: 0x80ee146b pfn: 0x80ee1
> [   47.349777] Machine check in kernel mode.
> [   47.353814] Data Write PLB Error