port-xen/53074: Daily 8.99.12 DOMU panic

[brad%anduin.eldar.org@localhost]

>Number:         53074
>Category:       port-xen
>Synopsis:       Daily 8.99.12 DOMU panic
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 05 18:10:00 +0000 2018
>Originator:     Brad Spencer
>Release:        NetBSD 8.99.12
>Organization:
	Eldar.org
>Environment:
System: NetBSD varda.nat.eldar.org 8.99.12 NetBSD 8.99.12 (XEN3_DOMU_ISCSI) #0: Thu Mar  1 22:43:01 EST 2018  brad%gimli.nat.eldar.org@localhost:/usr/src/sys/arch/amd64/compile/XEN3_DOMU_ISCSI amd64
Architecture: x86_64
Machine: amd64
>Description:
On a testing 64 bit DOMU running NetBSD 8.99.12 against a NetBSD 7.1_STABLE DOM0 I have a daily panic.  The ddb traceback is as follows:

panic: kernel diagnostic assertion "entry > NR_RESERVED_ENTRIES" failed: file "../../../../arch/xen/xen/xengnt.c", line 264 
cpu0: Begin traceback...
?() at ffffffff804f74b8
?() at ffffffff80600b95
?() at ffffffff802139eb
?() at ffffffff8022eb90
?() at ffffffff80212a48
?() at ffffffff80203119
?() at ffffffff804cd598
?() at ffffffff804b2ae6
?() at ffffffff8020f1a6
cpu0: End traceback...
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip 0xffffffff802057a5 cs 0xe030 rflags 0x202 cr2 0x7eb70853b020 ilevel 0x8 rsp 0xffffa0002c28fae8
curlwp 0xffffa00000c681a0 pid 10930.1 lowest kstack 0xffffa0002c28c2c0
Stopped in pid 10930.1 (ssh) at ffffffff802057a5:       leave
ds          0
es          faf8
fs          fa98
gs          fae8
rdi         6
rsi         a
rbp         ffffa0002c28fae8
rbx         104
rdx         1
rcx         0
rax         1
r8          ffffffff807373c0
r9          0
r10         75
r11         ffffa00000740048
r12         ffffffff80648e28
r13         ffffa0002c28fb30
r14         ffffa00000960000
r15         ffffa00000a57008
rip         ffffffff802057a5
cs          e030
rflags      202
rsp         ffffa0002c28fae8
ss          e02b
ffffffff802057a5:       leave
db{0}> 

The kernel used by this particular DOMU is just XEN3_DOMU plus the
iscsi support compiled in because module loading does not appear to
work.  The DOM0 is NetBSD 7.1_STABLE running Xen 4.5.1 in 64 bit.

>How-To-Repeat:
The DOMU lasts almost exactly 24 hours at a time.  Just wait and it
will happen again.  I can provide more information if it is desired.

>Fix:
No idea on the fix, just reporting.