On Thu, Oct 9, 2014 at 10:04 AM, Fengguang Wu <fengguang.wu@xxxxxxxxx> wrote:
> Hi Marek,
>
> FYI, we noticed the below changes on
>
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> commit 478e86d7c8c5f41e29abb81b05b459d24bdc71a2 ("mm: cma: adjust address limit to avoid hitting low/high memory boundary")
>
>
> +------------------------------------------+------------+------------+
> | | 81febe58a8 | 478e86d7c8 |
> +------------------------------------------+------------+------------+
> | boot_successes | 10 | 0 |
> | boot_failures | 5 | 10 |
> | kernel_BUG_at_arch/x86/mm/physaddr.c | 5 | |
> | invalid_opcode | 5 | |
> | EIP_is_at__phys_addr | 5 | |
> | Kernel_panic-not_syncing:Fatal_exception | 5 | |
> | backtrace:vm_mmap_pgoff | 5 | |
> | backtrace:SyS_mmap_pgoff | 5 | |
> | BUG:Int_CR2(null) | 0 | 10 |
> +------------------------------------------+------------+------------+
>
> [ 0.000000] BRK [0x025ee000, 0x025eefff] PGTABLE
> [ 0.000000] cma: dma_contiguous_reserve(limit 13ffe000)
> [ 0.000000] cma: dma_contiguous_reserve: reserving 31 MiB for global area
> [ 0.000000] BUG: Int 6: CR2 (null)
> [ 0.000000] EDI c0000000 ESI (null) EBP 41c11ea4 EBX 425cc101
> [ 0.000000] ESP 41c11e98 ES 0000007b DS 0000007b
> [ 0.000000] EDX 00000001 ECX (null) EAX 41cd8150
> [ 0.000000] vec 00000006 err (null) EIP 41072227 CS 00000060 flg 00210002
> [ 0.000000] Stack: 425cc150 (null) (null) 41c11ef4 41d4ee4d (null) 13ffe000 41c11ec4
> [ 0.000000] 41c2d900 (null) 13ffe000 (null) 4185793e 0000002e 410c2982 41c11f00
> [ 0.000000] 410c2df5 (null) (null) (null) 425cc150 00013efe (null) 41c11f28
> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-next-20141008 #815
> [ 0.000000] 00000000 425cc101 41c11e48 41850786 41c11ea4 41d2b1db 41d95f71 00000006
> [ 0.000000] 00000000 c0000000 00000000 41c11ea4 425cc101 41c11e98 0000007b 0000007b
> [ 0.000000] 00000001 00000000 41cd8150 00000006 00000000 41072227 00000060 00210002
> [ 0.000000] Call Trace:
> [ 0.000000] [<41850786>] dump_stack+0x16/0x18
> [ 0.000000] [<41d2b1db>] early_idt_handler+0x6b/0x6b
> [ 0.000000] [<41072227>] ? __phys_addr+0x2e/0xca
> [ 0.000000] [<41d4ee4d>] cma_declare_contiguous+0x3c/0x2d7
> [ 0.000000] [<4185793e>] ? _raw_spin_unlock_irqrestore+0x59/0x91
> [ 0.000000] [<410c2982>] ? wake_up_klogd+0x8/0x33
> [ 0.000000] [<410c2df5>] ? console_unlock+0x448/0x461
> [ 0.000000] [<41d6d359>] dma_contiguous_reserve_area+0x27/0x47
> [ 0.000000] [<41d6d4d1>] dma_contiguous_reserve+0x158/0x163
> [ 0.000000] [<41d33e0f>] setup_arch+0x79b/0xc68
> [ 0.000000] [<4184c0b4>] ? printk+0x1c/0x1e
> [ 0.000000] [<41d2b7cf>] start_kernel+0x9c/0x456
> [ 0.000000] [<41d2b2ca>] i386_start_kernel+0x79/0x7d
>
I notice that code has been merged into mainline kernel without fix,
maybe fengguang's mail was missed.
I review the code, dma_contiguous_reserve() is called before initmem_init(),
so the variable high_memory is not initialized and calculated by
__pa(high_memory),
in x86 arch high_memory is initialized after dma_contiguous_reserve(), while
in arm arch high_memory is initialized before dma_contiguous_reserve(),
I think that is the reason which causes the BUG in x86.
However, I'm not familiar with system init sequence, so I send this
notice mail rather than a patch :-(
cc more people
>
> Thanks,
> Fengguang
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