[vfio-users] Minimal host with desktop guest and gaming guest. Is this possible?

[almer]

> Yes, it's possible, not even hard.

Ok, so this isn't a hazy unattainable dream, perfect!


> unbind cards or unload the module and RX 480

The host would get the IGP from the CPU. Both PCIE cards would be
vfio-stubed, so as far as I understand it these cards will be handled by
the vfio module in the host kernel and should be freely assignable to
guests. Therefore don't use any power if no guest is using it.
I'm not deadset on Nvidia I rather would use something else because of the
uncertainty that comes with and Nvidia driver. My guess is that their
proprietary Nvidia linux driver would have VM detection too, but didn't
find confirmation on this. I would like to use a AMD graphics card just to
be safe and out of that armsrace, AMDs driver doesn't block like Nvidia
does.
But I got discouraged by AMD graphics card PCIE reset issue reports and I
couldn't make heads and tails about it. If any RX 480 works, great. I will
have to look more into this.


> My Linux desktop get the IGD [..] Why not make more use of IGD assignment
> in your configuration.

Does a host system even boot with all graphics devices stubed? So am I
right to assuming that x86 "graphic needs" are satisfied for POST but after
that doesn't care what happens to the graphics devices afterwards? I don't
mind a headless host at all, it will change somewhat how I setup things for
crypto/storage but that I can solve.
For the IGP to be stubed and passed through I need a ACS capable CPU? As it
seems I wrongfully assumed that Vt-d and Vt-x support entailed this.


> Concerns with your hardware choice otherwise: a) No ACS, you won't be
able
> to assign cards in CPU root port slots to separate VMs
> (see vfio.blogspot.com), b) insufficient cores, how much are you
> willing to have your storage server interfere with your gaming
performance?

a) Ok, I found your article http://vfio.blogspot.de/2015/
10/intel-processors-with-acs-support.html these are the only choices?
Doesn't AMD support this too? AMD CPUs are usually weaker in single core
performance, so I ignored AMD CPUs for years. But seeing the prices I
wonder if they have an alternative for ~450 Euro price range. Some of the
Intel CPUs you listed are way out of my budget. The strongest and somewhat
affordable listed is a i7-6850k. AMD ryzen 1800x costs ~470 Euro, but
doesn't have an IGP and I didn't look into AMD CPUs at all so I don't know
if they support ACS it has AMD-V tho.

b) Well. I'm used to Intel quad core CPUs. Seeing that no matter what I buy
I will endup with 6 cores at least, I guess I can live with it. Desktop
guest and host heavyload-PIDs will get taskset to one core and the gaming
guest gets the rest pinned and taskset. So my guess is that any
crypt/storage/desktop spike shouldn't be noticed in the gaming guest.


> The only major issue is that running things involving sound and video
becomes
> not possible on such desktop. But those can be viewed/listened locally, on
> whatever actual machine you happen to be at. (Or also there are ways to
pass
> through sound from a remote desktop, or use video-efficient protocols
such as
> SPICE, but for my use I did not look into those as of yet).

This would be an issue. I didn't look into audio and microphone that much.
I would like to hear the audio from desktop guest and gaming guest and have
microphone available at least in the gaming guest for voice chat. Right now
this doesn't matter that much. Host and guests will be all GNU/Linux
distributions so without having looked into it further I guess there is a
server solution if any audio/mic passthrough scenario wouldn't work. I
guess your SPICE suggestion is such a solution.
Monitor wise I initially thought about HDMI switching host and desktop
guest, but as it seems that I can vfio-stub all graphics devices with a
proper CPU, I won't need the passive PCIE card in the case of i7-6850k
anymore and can use the IGP for the desktop guest instead. The desktop
guest will be dual monitor setup and the gaming guest will be switched on
one of the monitors, like I have it right now with separate computers.
Keyboard + mouse, I already use a two port usb switch. I guess I can still
use that to switch between desktop and gaming guests, after one of the two
usb-switch cables is passed through to the desktop guest after boot.



I'm exited and a bit confused.

How do you see if a CPU does support proper isolation or not? It isn't the
feature list like AMD-V or Vt-d/x only. Is it a combination of mainboard
chipset and CPU? I ask because I see the TDP wattage difference between
ryzen 7 1800x and the i7-6850k. So being relatively equal in price and
performance I tend towards the ryzen CPU. In the last couple hours I fail
to find if it would support proper PCIE isolation or not. In the search
stumbled upon ACS kernel patch, if possible I don't want to apply the ACS
patch to the host kernel.
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