Bug 475780 - Kernel oops in paravirtualized xen: IP: [<d0833ec7>] :xen_blkfront:backend_changed+0x262/0x31d
Kernel oops in paravirtualized xen: IP: [<d0833ec7>] :xen_blkfront:backend_ch...
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
All Linux
medium Severity high
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Assigned To: Xen Maintainance List
Fedora Extras Quality Assurance
Depends On:
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Reported: 2008-12-10 08:27 EST by Jan ONDREJ
Modified: 2009-12-18 02:14 EST (History)
4 users (show)

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Fixed In Version:
Doc Type: Bug Fix
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Clone Of:
Last Closed: 2009-12-18 02:14:35 EST
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RHEL 7.3 requirements from Atomic Host:
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Description Jan ONDREJ 2008-12-10 08:27:38 EST
Description of problem:
After upgrade from Fedora 9 to Fedora 10 one paravirtualized xen server still shows error.

Version-Release number of selected component (if applicable):
Same problem for:

No problem on fc9 kernels.

How reproducible:
Always on one machine, never on others.

Steps to Reproduce:
I think it's problematic to reproduce on your machine.
I have this problem only on one virtual machine, other virtual machines on same server works well. My server is an x86_64 Fedora 8 with update kernel-xen:

Linux vs2.upjs.sk #1 SMP Thu Aug 7 12:44:22 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux

Actual results:

Mounting proc filesystem
Mounting sysfs filesystem
Creating /dev
Creating initial device nodes
blkfront: xvda: barriers enabled
 xvda: xvda1
BUG: unable to handle kernel NULL pointer dereference at 00000000
IP: [<d0833ec7>] :xen_blkfront:backend_changed+0x262/0x31d
*pdpt = 00000000a7c25027
Oops: 0000 [#1] SMP
Modules linked in: xen_blkfront(+)

Pid: 15, comm: xenwatch Not tainted ( #1)
EIP: 0061:[<d0833ec7>] EFLAGS: 00010246 CPU: 0
EIP is at backend_changed+0x262/0x31d [xen_blkfront]
EAX: cf848800 EBX: cf848800 ECX: d0833c65 EDX: 00000000
ESI: cf848800 EDI: cfc8c000 EBP: cf847f8c ESP: cf847f54
 DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
Process xenwatch (pid: 15, ti=cf847000 task=cf854010 task.ti=cf847000)
Stack: 00000000 c07a702f cf848800 cfc88080 d083546c cf847f8c c057836e 00000000
       cebf8000 c076fb3f c07a702f cf848800 cfc88080 d083546c cf847fa0 c057a2ba
       cf848810 cfc88000 cf847fc4 cf847fd0 c057931f cf847fb0 00000000 00000000
Call Trace:
 [<c057836e>] ? xenbus_read_driver_state+0x1e/0x31
 [<c057a2ba>] ? otherend_changed+0x65/0x6a
 [<c057931f>] ? xenwatch_thread+0xd7/0xff
 [<c0442d3a>] ? autoremove_wake_function+0x0/0x33
 [<c0579248>] ? xenwatch_thread+0x0/0xff
 [<c0442a97>] ? kthread+0x3b/0x61
 [<c0442a5c>] ? kthread+0x0/0x61
 [<c04098f7>] ? kernel_thread_helper+0x7/0x10
Code: 84 89 00 00 00 83 4e 44 08 e9 80 00 00 00 8b 07 ff 70 08 68 41 43 83 d0 6a ed 50 e8 01 48 d4 ef 83 c4 10 e9 b6 00 00 00 8b 57 04 <8b> 02 c1 e0 14 0b 42 04 e8 66 4c c8 ef 85 c0 89 c3 75 10 68 51
EIP: [<d0833ec7>] backend_changed+0x262/0x31d [xen_blkfront] SS:ESP 0069:cf847f54
---[ end trace 699266966296a986 ]---

Expected results:
Clean boot.

Additional info:
It's possible, that it is a problem of fedora-8 kernel-xen, but I am not sure.

Also tryed to rerun mkinitrd as described in bug#429937 without succes.

After this error system boots normally, but there is NO link on eth0, I can't use network connection on this virtual server.
Comment 1 Jan ONDREJ 2008-12-10 09:15:31 EST
After this chnage of my xen config works well:

disk = [

Commenting out CDROM let's me boot this machine without problems.
May be there is an problem with CDROM driver.

So now it's possible, that you can reproduce this problem on your machine.
Comment 2 Chuck Ebbert 2008-12-15 04:09:28 EST
Where do the xen drivers come from? They're not part of the kernel package AFAICT.
Comment 3 Chris Lalancette 2008-12-15 11:26:36 EST
    FYI; those Xen blkfront kernel drivers are indeed in the base kernel.  The block driver lives under drivers/block/xen-blkfront.c, the network driver lives under drivers/net/xen-netfront.c, and common xen stuff lives under drivers/xen

Chris Lalancette
Comment 4 Jan ONDREJ 2009-01-30 08:13:47 EST
Same problem on 2.6.29:
Comment 5 Mark McLoughlin 2009-01-30 10:56:58 EST
jan: thanks for the report; could you send the stack trace to the xen-devel list to see if anyone there has any input?
Comment 6 Jan ONDREJ 2009-01-30 12:53:03 EST
(In reply to comment #5)
> jan: thanks for the report; could you send the stack trace to the xen-devel
> list to see if anyone there has any input?

Which "stack trace"? This from bugreport or one created byt "echo t > /proc/sysrq-trigger" ?

My kernel continues to work normally, just without network connection, so when is the right time to create trace?
Comment 7 Bug Zapper 2009-11-18 03:01:11 EST
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Comment 8 Bug Zapper 2009-12-18 02:14:35 EST
Fedora 10 changed to end-of-life (EOL) status on 2009-12-17. Fedora 10 is 
no longer maintained, which means that it will not receive any further 
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