[Xen-devel] how I can set up an environment to debug PV guest and xen hypervisor

[Long Wang <longwang.longwang@xxxxxxxxx>]

Hi,

I am working on a project (a research project in my PhD thesis). The
project involves instrumentation into the source code of xen
hypervisor and Dom0. But now PV guests crash again and again. I need
to debug this project. I really need your help on how setting up an
environment to debug PV guest and xen hypervisor.

1) Here is the basic information about my testbed:
x86 32bit CPU
PV guest
Xen 3.3.1 + Linux 2.6.18 (comes with xen)
I built xen, Dom0 kernel, and DomU kernel by running
make world KERNELS=”linux-2.6-xen0 linux-2.6-xenU”

2) Here is more information on my problem:

> - Does dom0 start?
Yes.

> - Is the problem only with domU ?
The current failure is with domU. But because in my project I added
some code in the hypervisor, I expect that there might be some
hypervisor error in the future. I need a way to debug both the domU
and the hypervisor, or two separate ways: one for debugging the domU
and the other for debugging the xen hypervisor.

> - What's the problem/error?
I added code in the hypervisor to do some monitoring work in my
project (my code monitors some behavior of the hypervisor). Now after
the domU boots and I run a program in the domU, the domU crashes
immediately. So I really want to know how you guys set up an
environment and debug the domU (PV guest) and the xen hypervisor.

> - Please provide full logs showing the error messages.
The domU reports the following error log (dom0 does not report any error):

BUG: scheduling while atomic: swapper/0x00010000/0
 [<c0105b2b>] show_trace+0x1b/0x20
 [<c01061c6>] dump_stack+0x26/0x30
 [<c02daca6>] schedule+0x576/0x8a0
 [<c010312a>] cpu_idle+0x7a/0xc0
 [<c0102405>] rest_init+0x35/0x40
 [<c0360891>] start_kernel+0x371/0x410
 [<00000000>] _stext+0x3fefe000/0x60
BUG: unable to handle kernel paging request at virtual address 00003101
 printing eip:
c035bf27
00691000 -> *pde = 00000000:0102a001
03fc7000 -> *pme = 00000000:00000000
Oops: 0002 [#1]
SMP
Modules linked in:
CPU:    0
EIP:    0061:[<c035bf27>]    Not tainted VLI
EFLAGS: 00010096   (2.6.18 #5)
EIP is at 0xc035bf27
eax: 00003101   ebx: c01206d8   ecx: c031b2c0   edx: c01013a7
esi: c038d420   edi: 00000400   ebp: c02ee850   esp: c035be9f
ds: 007b   es: 007b   ss: 0069
Process swapper (pid: 0, ti=c035a000 task=c031b2c0 task.ti=c035a000)
Stack: 000100c0 00000000 35bf3c00 3551a0c0 00010001 00000100 35bee800 141d6fc0
      000100c0 35bf3c00 0bf580c0 000000c1 3551c800 35bf3cc0 0bf580c0 000100c1
      35bf3c00 000000c0 35bf0400 1071d2c0 bf221cc0 00002393 09100000 000000c1
Call Trace:
 [<c0105ab1>] show_stack_log_lvl+0xb1/0xe0
 [<c0105ce6>] show_registers+0x1b6/0x240
 [<c0105ead>] die+0x13d/0x310
 [<c011433d>] do_page_fault+0x7ed/0xf51
 [<c01055db>] error_code+0x2b/0x30
Code: 00 00 00 00 00 00 00 00 18 bf 35 c0 bb 0a 12 c0 50 e8 2e c0 24 bf


long

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