[Xen-devel] VM Crash when Xen open page sharing

[pengfei zhang <zpfalpc23@xxxxxxxxxxx>]

Hi all,
Recently, I try to fix the bugs of xen memory sharing and now it nearly
works. I boot 28 VM(RHEL5.4, 4 VCPUS and 512M memory) in every 20s, and
reboot each one in 10 mins, and find that it saves 4G for Xen when I use "xm
info".

But sometimes in my test, it encounter VM crashes, after viewing  the kernel
stack backtrace of VM, I find it crash on the same point!
Here come the kernel stack backtrace:

crash> bt -l
PID: 1682   TASK: ffff81001cc727e0  CPU: 1   COMMAND: "setfont"
 #0 [ffff810018f5f900] xen_panic_event at ffffffff88001d28
 #1 [ffff810018f5f920] notifier_call_chain at ffffffff80066eaa
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/kernel/sys.c:
146
 #2 [ffff810018f5f940] panic at ffffffff8009094a
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/kernel/panic.c:
101
 #3 [ffff810018f5fa30] oops_end at ffffffff80064fca
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/arch/x86_64/kernel/traps.c:
539
 #4 [ffff810018f5fa48] zone_statistics at ffffffff800caabe
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/mm/vmstat.c: 372
 #5 [ffff810018f5fac8] zone_statistics at ffffffff800caabe
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/mm/vmstat.c: 372
 #6 [ffff810018f5fb30] error_exit at ffffffff8005dde9
    include/linux/bitops.h: 42
    [exception RIP: vgacon_do_font_op+363]
    RIP: ffffffff800515e5  RSP: ffff810018f5fbe8  RFLAGS: 00010203
    RAX: 0000000000000000  RBX: ffffffff804b3740  RCX: ffff8100000a056d
    RDX: 000000000000056e  RSI: ffff81001c458000  RDI: ffffffff803244c4
    RBP: ffff81001c458000   R8: d0d6999996000000   R9: 0000009090b0b0ff
    R10: 0000000000000000  R11: 0000000000000000  R12: 0000000000000004
    R13: 0000000000000001  R14: 0000000000000001  R15: 000000000000000e
    ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
 #7 [ffff810018f5fbe0] vgacon_do_font_op at ffffffff800514e5
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/drivers/video/console/vgacon.c:
1078
 #8 [ffff810018f5fc20] vgacon_font_set at ffffffff8016bec5
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/drivers/video/console/vgacon.c:
1238
 #9 [ffff810018f5fc60] con_font_op at ffffffff801aa86b
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/drivers/char/vt.c:
3645
#10 [ffff810018f5fcd0] vt_ioctl at ffffffff801a5af4
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/drivers/char/vt_ioctl.c:
965
#11 [ffff810018f5fd70] tty_ioctl at ffffffff80038a2c
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/drivers/char/tty_io.c:
3340
#12 [ffff810018f5feb0] do_ioctl at ffffffff800420d9
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/fs/ioctl.c: 39
#13 [ffff810018f5fed0] vfs_ioctl at ffffffff800302ce
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/fs/ioctl.c: 500
#14 [ffff810018f5ff40] sys_ioctl at ffffffff8004c766
    /usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/fs/ioctl.c: 520
#15 [ffff810018f5ff80] system_call at ffffffff8005d116
   
/usr/src/redhat/BUILD/kernel-2.6.18/linux-2.6.18.x86_64/arch/x86_64/kernel/entry.S
    RIP: 00000039294cc557  RSP: 00007fff63bcf668  RFLAGS: 00010206
    RAX: 0000000000000010  RBX: ffffffff8005d116  RCX: 0000000000000000
    RDX: 00007fff63bcf600  RSI: 0000000000004b72  RDI: 0000000000000003
    RBP: 000000001b7d8ab0   R8: 0000000000000010   R9: 0000000000800000
    R10: 0000000000000000  R11: 0000000000000246  R12: 0000000000000010
    R13: 0000000000000200  R14: 0000000000000008  R15: 0000000000000008
    ORIG_RAX: 0000000000000010  CS: 0033  SS: 002b

the VM redhat kernel is from
http://rhkernel.org/kernelrpmsRHEL5/kernel-2.6.18-164.el5.src.rpm

Can some one help me with this problem? Thx!
                       --pengfei zhang

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