[vfio-users] VMs slow to a crawl with physical hardware attached

[Hristo Iliev]

On Tue, 19 Jan 2016 16:20:15 +0000 Curlen M <curl2k1 at gmail.com> wrote:

> Current install is Arch with kernel 4.3.3
> 

Hi,

Try using the linux-vfio-lts kernel from AUR. It is based on 4.1.x and
currently is the only kernel that works for me on my setup (same chipset, CPU,
and amount of memory as yours). Kernel 4.2 and newer have buggy virtual MTRR
implementation that results in VMs booting extremely slowly:

https://bugzilla.kernel.org/show_bug.cgi?id=107561

Check if that is the case by reducing the memory of the VM to 2 GiB - it
should then boot normally. Kernel 4.4 is supposed to bring the fix.

Regards,
Hristo

> On Tue, Jan 19, 2016 at 11:11 AM Will Marler <will at wmarler.com> wrote:
> 
> > What's your host OS/kernel version/etc ?
> >
> > On Tue, Jan 19, 2016 at 8:59 AM, Curlen M <curl2k1 at gmail.com> wrote:
> >  
> >> For the past month, I've been trying to get passthrough to work
> >> smoothly.  Needless to say, I haven't been successful.  I've tried various
> >> distros, and even rebuilt/upgraded my rig from Z97 to X99 (tbh, I've been
> >> wanting to do that anyway  :-D) thinking things would go smoother.  No
> >> dice.  Here's what I'm currently using:
> >>
> >> ASRock X99 Professional (the Gigabyte and Asus I had before these were
> >> worse)
> >> i7 5820k
> >> 32GB RAM
> >> Lots-o-drives
> >> 660Ti
> >> 680
> >> Fury X
> >>
> >> The setup has both VT-x and VT-d enabled and is booting with the CSM
> >> disabled.  All 3 GPUs are starting in UEFI GOP mode.
> >>
> >>
> >> The initial plan was to use the 660Ti for the host and assign vfio to the
> >> 680 for a SteamOS instance and the Fury for a W10 instance.  Haven't had
> >> any issues assigning these.  So I'm good here.
> >>
> >> I'm able to build the VMs using Virt-Manager and get the OS installed.
> >> But as soon as I shutdown the VM and assign a video card to either VM and
> >> start it up.  CPU utilization on the host shoots through the roof and the
> >> OS slows to a crawl (noticed this by starting top on accident).  I'm
> >> talking an hour or more to get to the windows 10 desktop.
> >>
> >> I've tried many different configurations (including Seabios and Gerd's
> >> OVMF).  Including removing the Fury from the system and attempting to use
> >> the 680 in W10 and vice versa.  I've tried ditching Virt-Manager and
> >> libvirtd and using Qemu start scripts.
> >>
> >>
> >> I've since dropped the 660Ti out of the mix and have been attempting to
> >> use the 680 as the host with the Fury for W10.  Same results.
> >>
> >>
> >> Anyone have any tips?  Ideas?  Anything?
> >>
> >> _______________________________________________
> >> vfio-users mailing list
> >> vfio-users at redhat.com
> >> https://www.redhat.com/mailman/listinfo/vfio-users
> >>
> >>  
> >