Re: kern/57199: Pure PVH i386 guests hang on disk activity

[Brad Spencer <brad%anduin.eldar.org@localhost>]

This is still 100% reproducable in 10.0 built from source as of
2024-03-28.

Config file:
kernel = "/lhome/xen/kernels/NetBSD_10.x/NetBSD_10_branch_20240328/i386/netbsd-GENERIC"
memory = 512
cpu_weight = 32
name = "nbsd10test32bit"
type="pvh"
vcpus = 1
vif = [ 'mac=aa:00:00:50:07:f4, bridge=bridge4' ]
disk = [ 'phy:/dev/mapper/rustvg0-nbsd10test32bitlv0,0x01,w' ]
root = "xbd0"


nbsd10test32bit# uname -a
NetBSD nbsd10test32bit 10.0 NetBSD 10.0 (GENERIC) #0: Sat Mar 30 22:01:46 EDT 2024  brad%samwise.nat.eldar.org@localhost:/lhome/NetBSD_10_branch_20240328/i386/OBJ/sys/arch/i386/compile/GENERIC i386

Create a tar archive that is fairly big.  It is likely that the larger
sets will work, but what I used was a tar archive from the userland of
the system itself (something like: cd /;tar -cf /var/tmp/distball.tar
./bin ./lib ./sbin ./usr ./stand).  I placed this in /var/tmp and called
it distball.tar

Create a directory in the path /var/tmp/Q and cd there.

Untar the archive..  something like:  tar -xvpf ../distball.tar

The untar will work for a short time and then hang up.  A CTRL-T
produces this:
x ./usr/libexec/cc1obj[ 115.0723697] load: 0.15  cmd: tar 1854 [uvnfp2] 0.04u 0.14s 0% 5340k
[ 116.9523882] load: 0.13  cmd: tar 1854 [uvnfp2] 0.04u 0.14s 0% 5340k
[ 118.0724972] load: 0.13  cmd: tar 1854 [uvnfp2] 0.04u 0.14s 0% 5340k
[ 118.6725079] load: 0.13  cmd: tar 1854 [uvnfp2] 0.04u 0.14s 0% 5340k


If I ran the same test with 1GB of memory it get a little further along,
but still hangs up:
x ./usr/libexec/postfix/scache[  66.3212543] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  67.1712694] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  67.3612609] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  68.2412022] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  68.4512385] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  68.6312665] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  68.8012961] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  68.9713106] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k
[  69.1213030] load: 0.34  cmd: tar 1977 [biowait] 0.04u 0.20s 0% 5344k


When the system is hung up, trying to log into the console will stick
after entering the username.  You can get into ddb from the console.

A PV+PVSHIM kernel of the same generation of source will work just fine
with the same test.