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Subject: Re: Early boot panic on machine with lots of memory
From: Yinghai Lu <yinghai@kernel.org>
To: Sasha Levin <levinsasha928@gmail.com>
Cc: Tejun Heo <tj@kernel.org>, Andrew Morton <akpm@linux-foundation.org>,
        David Miller <davem@davemloft.net>, hpa@linux.intel.com,
        linux-mm <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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On Thu, Jun 14, 2012 at 2:34 PM, Sasha Levin <levinsasha928@gmail.com> wrote:
> On Thu, 2012-06-14 at 13:56 -0700, Yinghai Lu wrote:
>> On Thu, Jun 14, 2012 at 2:50 AM, Sasha Levin <levinsasha928@gmail.com> wrote:
>> > On Thu, 2012-06-14 at 12:20 +0900, Tejun Heo wrote:
>> >> On Wed, Jun 13, 2012 at 11:38:55PM +0200, Sasha Levin wrote:
>> >> > Hi all,
>> >> >
>> >> > I'm seeing the following when booting a KVM guest with 65gb of RAM, on latest linux-next.
>> >> >
>> >> > Note that it happens with numa=off.
>> >> >
>> >> > [ ? ?0.000000] BUG: unable to handle kernel paging request at ffff88102febd948
>> >> > [ ? ?0.000000] IP: [<ffffffff836a6f37>] __next_free_mem_range+0x9b/0x155
>> >>
>> >> Can you map it back to the source line please?
>> >
>> > mm/memblock.c:583
>> >
>> > ? ? ? ? ? ? ? ? ? ? ? ?phys_addr_t r_start = ri ? r[-1].base + r[-1].size : 0;
>> > ?97: ? 85 d2 ? ? ? ? ? ? ? ? ? test ? %edx,%edx
>> > ?99: ? 74 08 ? ? ? ? ? ? ? ? ? je ? ? a3 <__next_free_mem_range+0xa3>
>> > ?9b: ? 49 8b 48 f0 ? ? ? ? ? ? mov ? ?-0x10(%r8),%rcx
>> > ?9f: ? 49 03 48 e8 ? ? ? ? ? ? add ? ?-0x18(%r8),%rcx
>> >
>> > It's the deref on 9b (r8=ffff88102febd958).
>>
>> that reserved.region is allocated by memblock.
>>
>> can you boot with "memblock=debug debug ignore_loglevel" and post
>> whole boot log?
>
> Attached below. I've also noticed it doesn't always happen, but
> increasing the vcpu count (to something around 254) makes it happen
> almost every time.
>
...
[    0.000000] memblock: reserved array is doubled to 512 at
[0x102febc080-0x102febf07f]
[    0.000000]    memblock_free: [0x0000102febf080-0x0000102fec0880]
memblock_double_array+0x1b0/0x1e2
[    0.000000] memblock_reserve: [0x0000102febc080-0x0000102febf080]
memblock_double_array+0x1c5/0x1e2

the reserved regions get double two times to 512.
....
> [ ? ?0.000000] ? ?memblock_free: [0x0000102febc080-0x0000102febf080] memblock_free_reserved_regions+0x37/0x39
> [ ? ?0.000000] BUG: unable to handle kernel paging request at ffff88102febd948
> [ ? ?0.000000] IP: [<ffffffff836a5774>] __next_free_mem_range+0x9b/0x155
> [ ? ?0.000000] PGD 4826063 PUD cf67a067 PMD cf7fa067 PTE 800000102febd160

that page table for them is

[    0.000000] kernel direct mapping tables up to 0x102fffffff @ [mem
0xc7e3e000-0xcfffffff]
[    0.000000] memblock_reserve: [0x000000c7e3e000-0x000000cf7fb000]
native_pagetable_reserve+0xc/0xe

only near by allocation is swiotlb.

[    0.000000] __ex_table already sorted, skipping sort
[    0.000000] memblock_reserve: [0x000000c3e3e000-0x000000c7e3e000]
__alloc_memory_core_early+0x5c/0x73
...
[    0.000000] memblock_reserve: [0x000000cfff8000-0x000000d0000000]
__alloc_memory_core_early+0x5c/0x73
[    0.000000] Checking aperture...

so the memblock allocation is ok...

can you please boot with "memtest" to see if there is any memory problem?

Thanks

Yinghai
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