linux-kernel - Re: Early boot panic on machine with lots of memory

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Date:	Fri, 15 Jun 2012 02:59:12 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>, hpa@...ux.intel.com,
	linux-mm <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm <kvm@...r.kernel.org>, avi@...hat.com,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: Early boot panic on machine with lots of memory

On Thu, 2012-06-14 at 16:57 -0700, Yinghai Lu wrote:
> On Thu, Jun 14, 2012 at 2:34 PM, Sasha Levin <levinsasha928@...il.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@...il.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?

The host got a memtest treatment, nothing found.

(I'll cc the KVM folks as well.)

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