[9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit Hypervisor

[9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit Hypervisor

[Kenneth L Van Alstyne]

Wow, thanks for the fast responses!

For what it's worth, the following is my Xen config:
kernel = "/home/kvanals/plan9/9xeninst-pae.gz"
memory = 32
vcpus = '1'
name = "plan9.kvanals.org"
vif = [ 'mac=00:16:3E:9F:FF:01' ]
disk = [ 'file:/home/kvanals/plan9/plan9.img,sda,w',
         'file:/home/kvanals/plan9/plan9.iso,sdb,r' ]
reboot = 'never'
extra="""
nobootprompt=local!/boot/bzroot
bootfile=sd01!cdboot!bootdisk.img
"""


Furthermore, this box only has 4GB of physical memory:
wired:~# xm info | grep total_memory
total_memory           : 4095

Mr. Miller:  I attempted to use your newly uploaded kernel, but was
greeted with a very similar panic:
wired:~# xm create -c /home/kvanals/plan9/boot.conf
Using config file "/home/kvanals/plan9/boot.conf".

Plan 9
127 holes free
0018a000 00dba000 12779520
12779520 bytes free
cpu0: 2792MHz AuthenticAMD AMD64 (cpuid: AX 0x20F51 DX 0x78BFBFF)
Started domain plan9.kvanals.org
                                panic: xenupdatema - pte 80184010 value
23c9b027
panic: xenupdatema - pte 80184010 value 23c9b027
dumpstack
ktrace /kernel/path 8001444c 80002e2c <<EOF
estackx 80003000
80002dcc=8001428d 80002dd8=80040836 80002ddc=8006bac4 80002de4=8006bb25
80002df0=80072d0c 80002e00=8004097d 80002e10=8006d0ba 80002e14=8001444c
80002e28=8001444c 80002e2c=80014291 80002e34=80040da3 80002e48=8006aa5a
80002e84=80073a0a 80002e90=80074844 80002ea4=80073c44 80002ed0=8006d0f9
80002ed4=8006aa5a 80002edc=80072d0c 80002ef0=80070200 80002ef4=80070206
80002f00=8006d0ba 80002f0c=8006d0ba 80002f10=80070438 80002f18=8007071c
80002f24=8006aa5a 80002f38=80070823 80002f44=8006c5a9 80002f60=8006cbf2
80002f8c=80011cc5 80002fac=80011be5 80002fb8=8001220a 80002fc4=80012256
80002fe4=00000000 80002fe8=801c5ff8 80002fec=80010a37 80002ff0=800b0147
80002ff4=00000000 80002ff8=8001001f 80002ffc=00000000
EOF
cpu0: exiting
cpu0: spurious interrupt 102, last 0
cpu0: spurious interrupt 102, last 0
cpu0: spurious interrupt 102, last 0
cpu0: spurious interrupt 102, last 0
...

Upon doing some "Googling" I came across one other mention of this problem
on 9fans, but it was never solved:
http://9fans.net/archive/2009/12/67


Thanks,
Kenny

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit Hypervisor

[Richard Miller]

> For what it's worth, the following is my Xen config:
> kernel = "/home/kvanals/plan9/9xeninst-pae.gz"
> memory = 32

32MB might be a bit tight - try 64.

> cpu0: spurious interrupt 102, last 0

You can stop these messages after a crash by adding *debug=1 to the
plan9.ini section of your config file.

I've put a new 9xeninst-pae.gz on sources with more diagnostic
output to help track down the panic.

Let's continue this off-list because not many people are
interested in xen.

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit Hypervisor

[Jano]

On Feb 10, 4:46 pm, 9f...@hamnavoe.com (Richard Miller) wrote:
> > For what it's worth, the following is my Xen config:
> > kernel = "/home/kvanals/plan9/9xeninst-pae.gz"
> > memory = 32
>
> 32MB might be a bit tight - try 64.
>
> > cpu0: spurious interrupt 102, last 0
>
> You can stop these messages after a crash by adding *debug=1 to the
> plan9.ini section of your config file.
>
> I've put a new 9xeninst-pae.gz on sources with more diagnostic
> output to help track down the panic.
>
> Let's continue this off-list because not many people are
> interested in xen.

oh? really?
Well, for one i am interested, so if you have continued off-list,
please cc me, i still have my amd64 xen host ready to host an plan9
guest if possible! I'd be so <stoked> to be able to finally have a
plan9 install!
Thanks,
John

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit

[Richard Miller]

Jano <sorosj@gmail.com>	Thu 11 Feb 09:55:
> ... if you have continued off-list,
> please cc me

Will do.  I'll also announce to the list when (if) we get it working.

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit

[Richard Miller]

> I'll also announce to the list when (if) we get it working.

It's working now.  Turned out to be a known error in xen 3.2 (hypervisor
was initialising the mmu page directory table incorrectly).  9xen kernels
on sources now have a simple workaround for this.

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit

[Jano]

On Feb 13, 11:20 am, 9f...@hamnavoe.com (Richard Miller) wrote:
> > I'll also announce to the list when (if) we get it working.
>
> It's working now.  Turned out to be a known error in xen 3.2 (hypervisor
> was initialising the mmu page directory table incorrectly).  9xen kernels
> on sources now have a simple workaround for this.

wow awesome!
I'll try it soon..
Thanks,
John

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit Hypervisor

[erik quanstrom]

> I've updated /n/sources/xen/xen3 source and sample kernels with a small
> mmu correction which was needed for Xen 3.4 (thanks to Peter Bosch for
> tracking down the bug).  Maybe this will help for your configuration too.
>
> How much physical RAM do you have?  I'm not aware of the PAE code having
> been tested with more than 4GB.  If your machine is bigger, you could
> try booting Xen with RAM restricted to, say, 2GB (should be a linux boot
> parameter for this) and see if it makes a difference.

could you explain this a little further.  pae would normally
not be useful with 2gb of ram and is often of dubious utility
on a 4gb machine.  what's different about xen?

- erik

Re: [9fans] Plan 9 on Xen 3.2.1 / 32-bit PAE Kernel / 64-bit

[Richard Miller]

> could you explain this a little further.  pae would normally
> not be useful with 2gb of ram and is often of dubious utility
> on a 4gb machine.  what's different about xen?

PAE is of no utility at all as far as I can see, but sometimes
we have to run xen guests on somebody else's hypervisor (think
virtual hosting companies).  If the hypervisor is configured
with PAE (or 64-bit, it seems), the guest has to run in PAE mode.

I hacked the Plan 9 xen kernel to support PAE for this reason,
but since my xen test machine has only a couple of gigs I have
never actually seen it work in the non-trivial case where the
upper half of a 64-bit page address is non-zero.  If our friend
has more than 4GB and the panic disappears when he uses less
than 2GB, that might indicate why he's having problems that
nobody else has seen.