port-xen/46013: uvm fault in printf_nolog() on MP Xen instance

[riz%NetBSD.org@localhost]

>Number:         46013
>Category:       port-xen
>Synopsis:       uvm fault in printf_nolog() on MP Xen instance
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Feb 12 23:00:00 +0000 2012
>Originator:     Jeff Rizzo
>Release:        NetBSD 5.99.65
>Organization:
        
>Environment:
        
        
System: NetBSD ip-10-248-67-207.us-west-2.compute.internal 5.99.65 NetBSD 
5.99.65 (EC2) #0: Sun Feb 12 13:57:10 PST 2012  
riz%breadfruit.tastylime.net@localhost:/home/riz/obj/sys/arch/amd64/compile/EC2 
amd64
Architecture: x86_64
Machine: amd64
>Description:
        While untarring src.tar.xz on an 8-vcpu Amazon EC2 instance, I ran
        into the following problem:


uvm_fault(0xffffffff8068cc20, 0xffffffff81400000, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff802ef14d cs e030 rflags 10206 cr2  
ffffffff81400000 cpl 0 rsp ffffa0013a253650
panic: trap
cpu1: Begin traceback...
printf_nolog() at netbsd:printf_nolog
startlwp() at netbsd:startlwp
alltraps() at netbsd:alltraps+0xab
uvm_pagermapin() at netbsd:uvm_pagermapin+0x179
genfs_getpages() at netbsd:genfs_getpages+0xc8a
VOP_GETPAGES() at netbsd:VOP_GETPAGES+0x4f
ufs_balloc_range() at netbsd:ufs_balloc_range+0xf7
ffs_write() at netbsd:ffs_write+0x2a6
VOP_WRITE() at netbsd:VOP_WRITE+0x37
vn_write() at netbsd:vn_write+0xf9
dofilewrite() at netbsd:dofilewrite+0x7d
sys_write() at netbsd:sys_write+0x62
syscall() at netbsd:syscall+0xc4
cpu1: End traceback...

dump to dev 142,17 not possible
rebooting...

I was preparing to test the fix for pr/45975, and had the patch in the
kernel I was running, but I have seen this problem before without the
patch as well.

>How-To-Repeat:
        tar --xz -x -f /var/tmp/src.tar.xz on a "cc1.xlarge" Amazon
        EC2 instance running NetBSD-current.  I don't believe there is
        anything particular to EC2, but this is the domU with the
        most vcpus I have run NetBSD on.  This particular dom0 was running
        Xen 3.4; I don't know about the other times I have encountered
        this issue.
>Fix:
        None given.

>Unformatted: