https://lists.ubuntu.com/archives/kernel-team/2016-December/081398.html
** Changed in: linux (Ubuntu Yakkety)
Status: New => In Progress
** Changed in: linux (Ubuntu Yakkety)
Assignee: Canonical Kernel Team (canonical-kernel-team) => Tim Gardner
(timg-tpi)
** Changed in: linux (Ubuntu)
Status: Triaged => Fix Released
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https://bugs.launchpad.net/bugs/1648873
Title:
Ubuntu 16.10 netboot install fails with "Oops: Exception in kernel
mode, sig: 5 [#1] " (lpfc)
Status in debian-installer package in Ubuntu:
New
Status in linux package in Ubuntu:
Fix Released
Status in debian-installer source package in Xenial:
New
Status in linux source package in Xenial:
Invalid
Status in debian-installer source package in Yakkety:
New
Status in linux source package in Yakkety:
In Progress
Bug description:
== Comment: #33 - Mauricio Faria De Oliveira - 2016-12-09 06:49:57 ==
Hi Canonical,
Can you please apply this patch [1] to 16.10 and 16.04.x HWE (4.8) ?
It's fixes a regression introduced in 4.8.
As you can see, it's in the SCSI maintainer (James Bottomley)'s
'fixes' branch, but didn't make 4.9-rc8 (maybe he considered it late
for this one).
We have installer, boot, and post-boot problems due to this one.
It'd be good if the netboot images for 16.04.x HWE kernel can get it too.
Thank you,
[1] scsi: lpfc: fix oops/BUG in lpfc_sli_ringtxcmpl_put()
http://git.kernel.org/cgit/linux/kernel/git/jejb/scsi.git/commit/?h=fixes&id=2319f847a8910cff1d46c9b66aa1dd7cc3e836a9
Historical context:
== Comment: #0 - HARSHA THYAGARAJA - 2016-11-21 02:39:35 ==
---Problem Description---
Ubuntu 16.10 netboot install fails with "Oops: Exception in kernel mode. "
(kernel: 4.8.0-27)
Machine Type = Power8 baremetal
---boot type---
QEMU direct boot kernel/initrd
---Kernel cmdline used to launch install---
On a Power8 server, Using kernel and initrd images,
netcfg/disable_dhcp=true netcfg/confirm_static=true
netcfg/choose_interface=98:BE:94:00:4C:68 netcfg/get_ipaddress=9.47.67.159/20
netcfg/get_gateway=9.47.79.254 netcfg/get_nameservers=
---Install repository type---
Internet repository
---Install repository Location---
http://ports.ubuntu.com/ubuntu-ports/dists/yakkety/main/installer-ppc64el/current/images/netboot/ubuntu-installer/ppc64el/
---Point of failure---
Other failure during installation (stage 1)
== Comment: #1 - HARSHA THYAGARAJA - 2016-11-21 02:41:54 ==
The netboot install fails and Call traces are seen at the Disk detection step.
== Comment: #8 - Mauricio Faria De Oliveira - 2016-11-21 15:58:25 ==
Finally got it.
The assembly offset/code + the trap signal is due to this BUG_ON(),
and the second condition triggered the trap.
Checking why piocb is not NULL but piocb->vport is NULL.
This might have happened in the lpfc_linkdown_port() path, in the stack trace.
Would need a more readable console log (ie, dmesg, as requested in
comments 5, 3) to help understanding it.
--
static int
lpfc_sli_ringtxcmpl_put(struct lpfc_hba *phba, struct lpfc_sli_ring *pring,
struct lpfc_iocbq *piocb)
{
lockdep_assert_held(&phba->hbalock);
BUG_ON(!piocb || !piocb->vport);
<...>
}
[ 226.147886] NIP [d00000000b7324c0]
lpfc_sli_ringtxcmpl_put+0x48/0x120 [lpfc]
0x2478 + 0x48 = 0x24c0 (tdnei; trap doubleword not equal immediate)
0000000000002478 <lpfc_sli_ringtxcmpl_put>:
<...>
2498: 78 2b bf 7c mr r31,r5 // r31 is *piocb (r5 is the
3rd function parameter)
249c: 78 1b 7d 7c mr r29,r3
24a0: 78 23 9e 7c mr r30,r4
24a4: 01 00 00 48 bl 24a4 <lpfc_sli_ringtxcmpl_put+0x2c>
// probably converted at module load time to the call lockdep_assert_held()
24a8: 00 00 00 60 nop
24ac: 00 00 bf 2f cmpdi cr7,r31,0 // compare piocb with 0.
checking for NULL.
24b0: 70 00 9e 41 beq cr7,2520
<lpfc_sli_ringtxcmpl_put+0xa8> // if equal to zero, branch out. done w/ the
former part of the OR check.
24b4: e8 00 3f e9 ld r9,232(r31) // an offset of piocb.
probably piocb->vport in the bug_on
24b8: 74 00 29 7d cntlzd r9,r9 // count leading zeroes. if r59
is null (0), leading zeroes is 64 (binary: 0100_0000, bit 6 is 1, and 6 LSbs
[bits 5-0] are 0)
24bc: 82 d1 29 79 rldicl r9,r9,58,6 // rotate left 58 (ie,
those 6 LSbs are now MSbs, and that bit 6 from 64 was rotated in the register
and is now bit 0, the LSb), now AND the 6 MSbs w/ 0-bits, and the all lower
bits with 1-bits (ie, save the LSb).
24c0: 00 00 09 0b tdnei r9,0 // trap if not equal to zero.
(ie, the whole r9 was zero, with 64 leading/consecutive zeroes, then bit 6 is
1, it becomes bit 0.. and since bit 0 is now 1, r9 is thus non-zero, and the
trap triggers.) this checked the latter part of the OR.
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