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netbsd dom0 + Xen 4.1 + netbsd pv domU + xl => works! (with caveat)
I just found out you can run a netbsd pv domU using the 'xl' command (vs
'xm'). hvm domu + xl has never been a problem. The caveat is this: the
disk(s) has to be of 'phy' type, as opposed to 'file' type. That is, in
the domU config file, instead of defining disk as such:
disk = [ 'file:/mnt/v01/vhosts/dadomu01/dadomu01.disk0.img,hda,w ]
the disk can be defined as such:
disk = [ 'phy:/dev/vnd0d,hda,w' ]
where vnd0 has been vnconfiged to point to the dadomu01.disk0.img file
above. I've also tested the config using an lvm logical volume and it
worked fine, and I would assume that any other physical device, like a
dk wedge would work as well.
I'm probably not the first one to find this out, however, I think it is
important to bring this up, especially since the last information that
I'm aware of on Xen 4, domU, and xl was this:
My understanding on the problem with netbsd dom0 + file based disk image
+ xl is that we don't have support for blktap and in that case xl will
start qemu-dm. In my case qemu-dm wasn't able to setup the disk image
file as a device (don't know why). The domU was shown to be in the 'b'
state, but I was unable to connect via console and the network was not
up either. This thread at the Xen ml gave me the idea of using phy disk
this is from Dec of 2010, I wonder what has changed since then.
Also, AFAIK, with xm and netbsd, the xenbackendd will use the
/usr/pkg/etc/xen/scripts/block sh script to setup the vnd device. I
wonder why the block script doesn't get executed when using xl. I guess
this is a part of xm + xend, since xl bypasses xend altogether. I don't
think we should go through the route of using qemu-dm since that's
another user process and I'd imagine the context switching would
dramatically affect disk io performance and plus we already have an
excellent kernel space vnd device. I think it's a matter of fixing some
glue logic, but what do I know. Should I file a PR to track this?
Btw, thanks to all of who have been working on improvements to netbsd +
xen, such as lvm and smp support in netbsd pv domu.
netbsd version: cvs co -D 2012.03.16.23.20.00 src
pkgsrc version: HEAD, about a day prior to pkgsrc-2012Q1
pv domu config:
name = "dadomu01"
kernel = "/mnt/v01/vhosts/dadomu01/netbsd-XEN3_DOMU.gz"
memory = 128
vcpus = 2
#disk = [ 'file:/mnt/v01/vhosts/dadomu01/dadomu01.disk0.img,hda,w',]
#disk = [ 'phy:/dev/dk1,hda,w' ]
#disk = [ 'phy:/dev/mapper/vg00-lv01,hda,w']
disk = [ 'phy:/dev/vnd0d,hda,w']
vif = [ 'mac=00:16:3e:55:cd:aa,bridge=bridge0' ]
on_reboot = 'restart'
on_crash = 'destroy'
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