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Re: [Xen-users] Multiseat workstation with one VM per user


2015-01-01 2:22 GMT+00:00 Gordan Bobic <gordan@xxxxxxxxxx>:
> On 2014-12-31 12:38, Luis P. Mendes wrote:
>> - base system (dom0) as lean as possible, just for Xen
> Trying to lean things out to a great extent is generally a
> waste of time. On any recent Linux distribution the base
> install is sufficiently large that it's losing game and
> saving a few GB of disk space is not worth the effort.
>> - one Slackware VM and one Ubuntu VM with direct access to hardware
>> via PV
> You need to clarify what exactly you mean by this. Getting
> hardware passthrough working at all can be hit and miss and
> is very hardware dependant. There are so many hardware and
> firmware bugs around that luck is a large factor in hardware
> selection.
I'd like to have both VMs in a Paravirtualized mode as in
with direct access to dedicated graphics card and usb controller or usb devices.

>> - other VMs for occasional use, which can run in virtualized hardware.
>> - three fanless graphic cards, for example AMD Radeon 6450. One for
>> base system (could be a cheaper one), and one dedicated (passthrough)
>> to Slackware VM, and similar for the third one for the Ubuntu VM.
>> Iâd be using HDMI as the output interface for the two VMs and VGA
>> for the base system, in case of necessity.
>>  I've read http://wiki.xen.org/wiki/Xen_VGA_Passthrough [1] and
>> http://wiki.xen.org/wiki/Xen_VGA_Passthrough_Tested_Adapters [2]
>> but still would like your opinions, as itâs my first time with Xen
>> and Iâm not fully aware of all the corners I could face.
> People's experience with ATI cards is at best mixed. I never got
> it fully working. Most people find it works OK on the first boot
> of the VMs, but as soon as you need to reboot VMs things fall
> apart pretty quickly with cards not being reinitialized properly
> on a reboot. That's on Windows VMs. With Linux VMs, a lot would
> depent on how up to the job the radeon driver is. Last I checked,
> it wasn't.
I've no experience with this, but always got the impression, from what
I've read, that nvidia proprietary blob was bettter than AMD ATI's on
Linux, but that open-source ATI radeon driver was better than
The reboot problem you mention is something I have to take into consideration.

> If all you are after is Linux-on-Linux kind of a setup, you would
> probably be a lot better off with something like LXC, OpenVZ or
> VServer for separating server tasks.
But AFAICT, Linux on  Linux should have the same OS and the same
Kernel (maybe it supports a kernel with a minor update difference).
As I want to have Slackware and Ubuntu, I don't think I can use LXC or
OpenVZ for that.

> If all you need is a multi-seat workstation, you don't need
> virtualization at all, you can just configure multiple Xorg
> instances to access different GPU/keyboard/mouse sets.
As stated above, as I want to have one system with Slackware and
another one with Ubuntu, I don't see any other way than to have

>> Now, what Iâd like to know:
>> 1. Is Slackware 14.1 or current with the xen package from
>> http://slackbuilds.org/repository/14.1/system/xen/ [3] as stable as
>> Slackware without it? Iâve been using Slackware for ten years as a
>> rock solid Linux. Would I gain anything in having another OS as dom0?
>> Is NetBSD up to the task?
> I think this is the first time I heard of anyone using Slackware in
> at least 10 years. Most people these days prefer to have a
> package management system in their OS.
Slackware does not give me any headache when installing programs,
although it has no built-in dependency management system.  There are
some efforts to accomplish this: https://github.com/dslackw/slpkg
But, in the past, I had problems with .deb and .rpm when I tried to
install programs not available as packages.  It's easier to install
them in Slackware, for me.

>> 6. Iâve read that itâs more stable to passthrough usb devices
>> individually, than usb host controllers. Is this still the case? As
>> Iâd like each of the two of us to have two USB 3.0 ports in
>> exclusivety.
> Passing USB devices has been hit and miss for me. Passing PCIe devices
> that are USB host controllers, on the other hand, has worked well.
Ok, better to know this.

>> 7. (repetition)  Is NetBSD with its lower power requirements up to
>> this task?
> There is no gain. Getting this kind of a setup to work reliably at
> all on OS-es that are used (and thus debugged) by thousands of people
> is difficult enough without getting bogged down in OS-es that only
> a handful of people use in a similar scenario.
>> In conclusion:
>> One workstation, with native disk and graphic card access to each of
>> the two main VMs running as fast as it they were native.
> As fast as native? Not going to happen. Fast enough? Sure. I have
> a triple seat gaming machine that works quite well, but that is
> very different from what you are proposing above (Nvidia GPUs,
> Windows guests)
So, for graphics do you get native performance with the passthrough?
But for the rest, are you able to measure how slower are the guest


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