[xen] FreeBSD Xen PVM DomU crashes

[Yury A. Buldakov]

FreeBSD environment: uname -a
FreeBSD pbox-xen-freebsd.silentnoise.intra 8.0-RC1 FreeBSD 8.0-RC1 #0 r:
Mon Oct  5 12:58:34 EEST 2009    
root at freebsd-8-buildbox.silentnoise.intra:/usr/obj/usr/src/sys/XEN  i386

I have nfs-shared /usr/ports. While making pkgdb -aF my freebsd domU
crashes:
panic: HYPERVISOR_mmuext_op(&op, 1, NULL, DOMID_SELF) < 0:
/usr/src/sys/i386/xen/xen_machdep.c:465
cpuid = 0
KDB: enter: panic
[thread pid 4695 tid 100078 ]
Stopped at      kdb_enter+0x3a: movl    $0,kdb_why
db>

But in most cases it crashes with the following:
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address    = 0x107
fault code        = supervisor read, page not present
instruction pointer    = 0x21:0xc01764e8
stack pointer            = 0x29:0xd59f883c
frame pointer            = 0x29:0xd59f883c
code segment        = base 0x0, limit 0xfffff, type 0x1b
            = DPL 1, pres 1, def32 1, gran 1
processor eflags    = interrupt enabled, resume, IOPL = 0
current process        = 18518 (sendmail)
[thread pid 18518 tid 100089 ]
Stopped at      strlen+0x8:     cmpb    $0,0(%edx)
db>
Tracing pid 18518 tid 100089 td 0xc2d876c0
strlen(107,d59f898c,0,d59f888c,c011a32b,...) at strlen+0x8
kvprintf(c035c5ae,c0108b80,d59f898c,a,d59f89cc,...) at kvprintf+0x8fe
vsnprintf(c03d3460,100,c035c5ae,d59f89cc,0,...) at vsnprintf+0x3b
panic(c035c5ae,107,c036d649,33e,16d,...) at panic+0x8d
_mtx_lock_flags(c076d808,0,c036d649,33e,c30dfc00,...) at
_mtx_lock_flags+0x9a
netisr_clearqdrops(d59f8a28,c2d87764,c0512828,0) at netisr_clearqdrops+0x66e
netisr_queue_src(1,0,c30dfc00,d59f8a6c,c01861ee,...) at
netisr_queue_src+0xa7
netisr_queue(1,c30dfc00,c30dfc48,d59f8af8,d59f8a80,...) at netisr_queue+0x20
if_simloop(c237b000,c30dfc00,2,0,c01a299f,...) at if_simloop+0xfe
looutput(c237b000,c30dfc00,d59f8b00,d59f8af8,c031fee4,...) at looutput+0x141
ip_output(c30dfc00,0,0,0,0,...) at ip_output+0x9cc
tcp_output(c273d768,c246b840,1b9,c26501a4,c2d8c19c,...) at tcp_output+0x1540
tcp_ctloutput(c2d8c19c,c246b840,c2d876c0,25,d59f8c70,...) at
tcp_ctloutput+0x933
soconnect(c2d8c19c,c246b840,c2d876c0,bf7fadc0,c246b840,...) at
soconnect+0x52
kern_connect(c2d876c0,6,c246b840,c246b840,ffffffff,...) at kern_connect+0xa6
connect(c2d876c0,d59f8d08,c,c0364398,c039d138,...) at connect+0x46
syscall(d59f8d48) at syscall+0x2a3
Xint0x80_syscall() at Xint0x80_syscall+0x22
--- syscall (98, FreeBSD ELF32, connect), eip = 0x283b9e5b, esp =
0xbf7fac5c, ebp = 0xbf7fae88 ---