NetBSD Problem Report #55607

From brad@anduin.eldar.org  Tue Aug 25 20:30:23 2020
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Date: Tue, 25 Aug 2020 16:30:18 -0400 (EDT)
From: brad@anduin.eldar.org
Reply-To: brad@anduin.eldar.org
To: gnats-bugs@NetBSD.org
Subject: Panic 9.0_STABLE Xen PV with ZFS module
X-Send-Pr-Version: 3.95

>Number:         55607
>Category:       kern
>Synopsis:       Panic 9.0_STABLE Xen PV with ZFS module
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Aug 25 20:35:00 +0000 2020
>Last-Modified:  Mon Jan 17 18:40:00 +0000 2022
>Originator:     brad@anduin.eldar.org
>Release:        NetBSD 9.0_STABLE
>Organization:
	eldar.org
>Environment:
System: NetBSD samwise.nat.eldar.org 9.0_STABLE NetBSD 9.0_STABLE (XEN3_DOMU) #0: Sat May  9 22:12:48 EDT 2020  brad@samwise.nat.eldar.org:/lhome/NetBSD_9_branch_20200509/amd64/OBJ/sys/arch/amd64/compile/XEN3_DOMU amd64
Architecture: x86_64
Machine: amd64
>Description:

I have been using ZFS with a 9.0_STABLE Xen PV system for some time
with pretty good results.  The last time that the system was updated
was 2020-05-09 and all was ok.  I went to update the system to
2020-08-20 and when the zfs module loads the DOMU guest panics with
this:

[   3.8500388] fatal page fault in supervisor mode
[   3.8500388] trap type 6 code 0x2 rip 0xffffffff8022abba cs 0xe030 rflags 0x10202 cr2 0xca000000eb ilevel 0x8 rsp 0xffff8c00d2063c30
[   3.8500388] curlwp 0xffff8c0007460040 pid 0.2 lowest kstack 0xffff8c00d20602c0
kernel: page fault trap, code=0
Stopped in pid 0.2 (system) at  netbsd:xbd_handler+0x223:       movl    $0x5,20(
%r13)
xbd_handler() at netbsd:xbd_handler+0x223
xen_intr_biglock_wrapper() at netbsd:xen_intr_biglock_wrapper+0x1d
evtchn_do_event() at netbsd:evtchn_do_event+0xe8
do_hypervisor_callback() at netbsd:do_hypervisor_callback+0x161
Xhypervisor_pvhvm_callback() at netbsd:Xhypervisor_pvhvm_callback+0xa0
idle_loop() at netbsd:idle_loop+0xb6
ds          16
es          b910
fs          0
gs          d3
rdi         6
rsi         ffff8c00d3556000
rbp         ffff8c00d2063ca0
rbx         1d
rdx         9a0
rcx         16
rax         ffff8c000846b910
r8          698
r9          32
r10         0
r11         246
r12         0
r13         ca000000cb
r14         ffffffffffffffff
r15         ffff8c000846b000
rip         ffffffff8022abba    xbd_handler+0x223
cs          e030
rflags      10202
rsp         ffff8c00d2063c30
ss          e02b
netbsd:xbd_handler+0x223:       movl    $0x5,20(%r13)

The zfs module from 2020-05-09 actually appears to work with the
2020-08-20 DOMU kernel and doesn't panic which may be suggestive of
something.

>How-To-Repeat:

Try using zfs in a very recent 9.0_STABLE

>Fix:

Don't know, except that -current appears to work fine.

>Audit-Trail:
From: Christian Kujau <lists@nerdbynature.de>
To: gnats-bugs@NetBSD.org
Cc: lists@nerdbynature.de
Subject: Re: kern/55607
Date: Mon, 17 Jan 2022 19:34:56 +0100 (CET)

 This still happens with 9.2_STABLE (XEN3_DOMU) when run as a Xen PV 
 DomU:

 $ doas zpool create test /dev/xbd2a
 fatal page fault in supervisor mode
 [  86.3298078] trap type 6 code 0x2 rip 0xffffffff8022ae1a cs 0xe030 rflags 0x10286 cr2 0x15300000174 ilevel 0x8 rsp 0xffffcf80790e3c30
 [  86.3298078] curlwp 0xffffcf8003a35040 pid 0.2 lowest kstack 0xffffcf80790e02c0
 [  86.3298078] panic: trap
 [  86.3298078] cpu0: Begin traceback...
 [  86.3298078] vpanic() at netbsd:vpanic+0x143
 [  86.3298078] snprintf() at netbsd:snprintf
 [  86.3298078] startlwp() at netbsd:startlwp
 [  86.3298078] alltraps() at netbsd:alltraps+0xae
 [  86.3298078] xen_intr_biglock_wrapper() at netbsd:xen_intr_biglock_wrapper+0x1d
 [  86.3298078] evtchn_do_event() at netbsd:evtchn_do_event+0xe8
 [  86.3298078] do_hypervisor_callback() at netbsd:do_hypervisor_callback+0x161
 [  86.3298078] Xhypervisor_pvhvm_callback() at netbsd:Xhypervisor_pvhvm_callback+0xa0
 [  86.3298078] idle_loop() at netbsd:idle_loop+0xb6
 [  86.3298078] cpu0: End traceback...
 [  86.3298078] dumping to dev 142,1 (offset=525199, size=0): not possible
 [  86.3298078] rebooting...

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