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From Tim Mackey <tmac...@gmail.com>
Subject Re: Support pure Xen as a hypervisor follow-up
Date Fri, 06 Jun 2014 16:22:48 GMT
If you can give me the commit ID for your HEAD, I'll check and see
what's up.  It could be another conflict needing resolution.

-tim

On Fri, Jun 6, 2014 at 12:16 PM, sebgoa <runseb@gmail.com> wrote:
>
> On Jun 6, 2014, at 5:17 PM, Tim Mackey <tmackey@gmail.com> wrote:
>
>> Dave,
>>
>> I've submitted a merge review request
>> (https://reviews.apache.org/r/22270/) yesterday.
>
> Unfortunately that patch did not seem to apply cleanly. I have not dug deep though..
>
>> If you want to avoid
>> having to potentially deal with a bunch of conflicts, you might want
>> to see if your patches apply cleanly there and let me know.  Happy to
>> help with any conflict resolution.
>>
>> btw, I didn't see a design document up on the
>> wiki(https://cwiki.apache.org/confluence/display/CLOUDSTACK/4.5+Design+Documents).
>> Can you get one there and start a DISCUSS thread?  It'll probably
>> tease out some gotchas you might not be aware of.
>>
>> -tim
>>
>> On Fri, Jun 6, 2014 at 11:04 AM, Dave Scott <Dave.Scott@citrix.com> wrote:
>>> Hi,
>>>
>>> Here’s a quick status update:
>>>
>>> On 16 May 2014, at 15:22, Dave Scott <Dave.Scott@citrix.com> wrote:
>>>
>>>> Hi,
>>>>
>>>> On 14 May 2014, at 09:53, sebgoa <runseb@gmail.com> wrote:
>>>>
>>>>>
>>>>> On Apr 9, 2014, at 2:37 PM, Dave Scott <Dave.Scott@citrix.com>
wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Following up from Tim's "Support pure Xen as a hypervisor" proposal
last month[1] I'd like to start working on this and maybe even make a little bit of progress
while I'm at CCC in Denver.
>>>>>>
>>>>>> Helpfully James Bulpin managed to get CS + libvirt + xen to start
an instance in a simple configuration. Although the patches[2] are not intended to be production-ready
:) they help highlight some of the areas we need to change.
>>>>>
>>>>> Dave, just to let you know that Tim has done some important "refactoring"
to split up XenServer hypervisor in CS between Xen and XenServer. That way we could keep using
xapi for XS but start moving to libvirt for Xen.
>>>>>
>>>>> Tim worked in the xen2server branch (don't ask about the name, I messed
it up…:) ).
>>>>>
>>>>> https://git-wip-us.apache.org/repos/asf?p=cloudstack.git;a=shortlog;h=refs/heads/xen2server
>>>>>
>>>>> Would be nice to see some of the libvirt stuff in that branch to handle
a new driver for Xen.
>>>>>
>>>>> Since the two hypervisors will be split up, we could still drop in some
early libvirt patches to handle Xen and put this in 4.5 as a wip.
>>>>
>>>> Thanks for the links.
>>>>
>>>> I’m slowly building up a set of patches here:
>>>>
>>>> https://github.com/djs55/cloudstack/tree/virsh-capabilities
>>>>
>>>> I think once I’ve gotten to a stable-ish point I’ll rebase on top of
Tim’s branch.
>>>>
>>>> So far I’ve
>>>> * changed the hypervisor detection to use ‘virsh capabilities’ in one
place and ‘cat /sys/hypervisor/type’ in another. Thinking about it again, I think it’s
probably best to standardise on /sys/hypervisor/type since that will succeed irrespective
of whether the libvirtd service is chkconfig’d on or not.
>>>>
>>>> * in the python cloudutils system setup stuff isKvmEnabled() has become isHypervisorEnabled()
>>>>
>>>> * added a XenLibvirtDiscoverer similar to the LXC one
>>>>
>>>> * fixed what I believe is a race in sshExecuteCmdOneShotWithExitCode (which
seems to hit me every time, I don’t know why other people seem to be immune from it): see
CLOUDSTACK-6621 and review board request 21261
>>>>
>>>> * added the new hypervisor to hypervisor.list and system.vm.default.hypervisor,
so it appears in the UI properly
>>>>
>>>> * registered a system VM template in the database, using the same qcow2 image
as KVM
>>>>
>>>> For my test host I’m using a XenServer nightly snapshot which comes with
a nice modern xen and kernel, and is easy to install bleeding-edge libvirt on top. I had to
tweak the kernel configuration and the network configuration but I’m hoping to make it work
out of the box in future.
>>>>
>>>> When I deploy my ‘datacenter’ the discovery phase works, the agent connects
and looks healthy in the logs and the UI. The next step is to figure out why the system VM
template isn’t being copied to primary storage — for some reason the copy isn’t being
attempted but I can’t see any obvious reason why.
>>>
>>> I’m now at the stage of getting my system VMs to start via libvirt. The main
missing feature is support for <channels>: low-bandwidth private host<->guest
control channels. These channels are generally useful things and are needed by other projects
(like oVirt), so I’d like to add them to libxl and libvirt’s libxl driver. There’s a
thread on xen-devel and libvir-devel if anyone’s interested:
>>>
>>> http://www.redhat.com/archives/libvir-list/2014-June/msg00180.html
>>>
>>> Once the <channels> are sorted, basic VM operations should work. The next
step would be to rebase my patches on top of Tim’s renaming changes and tidy them up for
review.
>>>
>>> Cheers,
>>> Dave
>>>
>>>>
>>>> Cheers,
>>>> Dave
>>>>
>>>>>
>>>>> -Sebastien
>>>>>
>>>>>>
>>>>>> Some of the areas are:
>>>>>>
>>>>>> 1. hypervisor detection
>>>>>>
>>>>>> Where we currently look for KVM specifically ("lsmod | grep kvm")
we could switch to either detecting any Linux hypervisor (by reading /sys/hypervisor/type)
and assuming if a hypervisor is present then we can use libvirt on it (is this a fair assumption?)
Or we could white-list “kvm” or “xen”. Or we could query libvirt directly (perhaps
via 'virsh capabilities'?)
>>>>>>
>>>>>> 2. fiddling with the domain.xml
>>>>>>
>>>>>> When starting a domain via libvirt the XML configuration has hypervisor-specific
stuff in it. Some of this is easy to change like:
>>>>>>
>>>>>> <domain type='kvm'>
>>>>>>
>>>>>> obviously becomes
>>>>>>
>>>>>> <domain type='xen'>
>>>>>>
>>>>>> and
>>>>>>
>>>>>> <emulator>/usr/libexec/qemu-kvm</emulator>
>>>>>>
>>>>>> should probably be
>>>>>>
>>>>>> <emulator>/some/other/path/qemu-dm</emulator>
>>>>>>
>>>>>> Some is a bit more invasive (to the VM) such as the virtual hardware
type should be switched from "virtio" to "xen" (and the block device in Linux will change
from /dev/vd* to /dev/xvd*) and we'll have to either implement or work around the lack of
>>>>>>
>>>>>> <channel type='unix'> ...
>>>>>>
>>>>>> -- I presume this is a control channel into the system VM. Perhaps
we could implement this in libvirt/libxl using vchan?
>>>>>>
>>>>>> 3. system VMs?
>>>>>>
>>>>>> It would be very convenient if the system VM images could work on
both xen and KVM. This is probably doable as long as we don't bake in virtual hardware specific
information (such as /dev/vda) in the image. We could use the qcow2 format in both cases.
What do you think?
>>>>>>
>>>>>> … and I’m sure there’s more.
>>>>>>
>>>>>> Anyway, feedback would be welcome. If anyone else in Denver wants
to chat, then come grab me later!
>>>>>>
>>>>>> Cheers,
>>>>>> Dave Scott
>>>>>>
>>>>>> [1] http://mail-archives.apache.org/mod_mbox/cloudstack-users/201403.mbox/%3cCAJGXtBNbmQTQ81rALgH2kMA7V5WJYZKr3xnyasMKC_br+UKzOw@mail.gmail.com%3e
>>>>>>
>>>>>> [2] https://github.com/jamesbulpin/cloudstack/commits/jamesb_xen_exploratory
>>>
>

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