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Re: [Xen-devel] Crash on boot with 2.6.37-rc8-git3

To: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Subject: Re: [Xen-devel] Crash on boot with 2.6.37-rc8-git3
From: M A Young <m.a.young@xxxxxxxxxxxx>
Date: Fri, 7 Jan 2011 20:34:43 +0000 (GMT)
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On Fri, 7 Jan 2011, Konrad Rzeszutek Wilk wrote:
BUG unable to handle kernel NULL pointer dereference at
IP: [<ffffffff81b69b92>] setup_node_bootmem+0x16b/0x199

Hmmm, I did see something similar to this in 2.6.37-rc1, but we fixed
that quickly. It was triggered by having 4GB of memory or so and
the work-around was to use dom0_mem=max:2GB.

Can you send the photo? Maybe the calleer stack will shed some light.

Here are two photos of the output at different times. The context is

   0xffffffff81b69b6d <setup_node_bootmem+326>:
    callq  0xffffffff81475ec9 <printk>
   0xffffffff81b69b72 <setup_node_bootmem+331>:   movslq %ebx,%rdx
   0xffffffff81b69b75 <setup_node_bootmem+334>:   xor    %eax,%eax
   0xffffffff81b69b77 <setup_node_bootmem+336>:   mov    $0x4fc0,%ecx
   0xffffffff81b69b7c <setup_node_bootmem+341>:
    mov    -0x7e4cb750(,%rdx,8),%rsi
   0xffffffff81b69b84 <setup_node_bootmem+349>:   shr    $0xc,%r13
   0xffffffff81b69b88 <setup_node_bootmem+353>:   shr    $0xc,%r12
   0xffffffff81b69b8c <setup_node_bootmem+357>:   sub    %r13,%r12
   0xffffffff81b69b8f <setup_node_bootmem+360>:   mov    %rsi,%rdi
   0xffffffff81b69b92 <setup_node_bootmem+363>:   rep stos %eax,%es:(%rdi)
   0xffffffff81b69b94 <setup_node_bootmem+365>:   mov    %ebx,%edi
   0xffffffff81b69b96 <setup_node_bootmem+367>:
    mov    -0x7e4cb750(,%rdx,8),%rax

which is somewhere around line 224 in arch/x86/mm/numa_64.c

        if (nid != nodeid)
printk(KERN_INFO " NODE_DATA(%d) on node %d\n", nodeid, nid);

        memset(NODE_DATA(nodeid), 0, sizeof(pg_data_t));
        NODE_DATA(nodeid)->node_id = nodeid;
        NODE_DATA(nodeid)->node_start_pfn = start_pfn;
        NODE_DATA(nodeid)->node_spanned_pages = last_pfn - start_pfn;


I do have 4GB of memory and the system does boot if I add dom0_mem=max:2GB to the xen boot line.

        Michael Young

Attachment: photo1.jpg
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