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[vfio-users] Attempting Multi-Seat crashes both VMs with assigned GPUs, unless the VMs are on a single disk with the OS



Hi all.

Pass-though works surprisingly well, unless I start a second VM with or without an assigned GPU.

It seems the only way I can multi-seat to work is by having the OS and the VMs on a single disk, and after weeks of futility I'm starting to wonder if I can even replicate that.

If I attempt to run the VMs concurrently the display driver will crash on one VM followed shortly by the other.  I've replicated this problem with multiple kernels from 4.2.1 to 4.7.X, and on two X58/LGA1366 MBs, so I suspect it affects most or all of them, at least when used with Debian / Proxmox.

There is nothing in the system logs to indicate why.

Here are the specs on the system I'm currently working on.

Distro:  Debian 8 / Proxmox 4.2
MB:  Asus Rampage III
CPU:  Xeon X5670
RAM:  24 GB

DISK1:  OS - XFS/LVM
DISK2-4:  VMs - ZFS RAIDZ-1

I've also seen the same on a GA-EX58 mb, set up identically.  I can test an Asus P658XD-E as well, and potentially a Rampage II


I've tried ZFS, MDADM with and without LVM, I've tried MDADM raids 5, 1, and even 0.

I thought for sure that in the worst case scenario I would be able to assign a VM per disk.  Not so.

Oddly, it's actually gotten worse in that before I would need to start something 3D on both VMs in order to reliably crash both VMs (within seconds of each other usually, someone may remember that post).  Now all I need to do is start the second one, and the display driver will crash on the first one. (The fact that both VMs always crash has to be indicative of something, but not sure what.)  If that second VM has a PCI device assigned, it will also crash.

I'm pretty much back at the drawing board.  I'm actually starting to doubt that my 'single disk test' really worked.  Maybe I just didn't run it long enough?  So I will try that again.  Unfortunately, I only have spindle disks large enough to hold everything on hand right now, so it won't be an exact replica.

Beyond that, I really don't know.  I currently have the system set up in almost the most basic way I can to have something acceptable:
-OS on a single 120 GB SSD
-VM Root Pool on 3 240 GB SSD, Raid Z-1

Soft rebooting a VM will always cause that VM's display to get garbled on POST.  I don't even have to get into Windows, if that happens I know the VM is beyond salvation, and the second one is going down too.

If it isn't the chipset and/or some nuance of Debian / Proxmox, a third possibility may be some server-oriented tuning cooked into Proxmox.  (Maybe I'll do single disk this time with regular Debian, and see if there is some change.)

Here are my invocations of KVM:

VM1:

# sed -e 's/#.*$//' -e '/^$/d' /root/src/brian.1
/usr/bin/systemd-run \
--scope \
--slice qemu \
--unit 110 \
-p KillMode=none \
-p CPUShares=250000 \
/usr/bin/kvm -id 110 \
-chardev socket,id=qmp,path=/var/run/qemu-server/110.qmp,server,nowait \
-mon chardev=qmp,mode=control \
-pidfile /var/run/qemu-server/110.pid \
-daemonize \
-smbios type=1,uuid=6a9ea4a2-48bd-415e-95fb-adf8c9db44f7 \
-drive if=pflash,format=raw,readonly,file=/usr/share/kvm/OVMF-pure-efi.fd \
-drive if=pflash,format=raw,file=/root/sbin/110-OVMF_VARS-pure-efi.fd \
-name Brian-PC \
-smp 12,sockets=1,cores=12,maxcpus=12 \
-nodefaults \
-boot menu=on,strict=on,reboot-timeout=1000 \
-vga none \
-nographic \
-no-hpet \
-cpu host,hv_vendor_id=Nvidia43FIX,hv_spinlocks=0x1fff,hv_vapic,hv_time,hv_relaxed,+kvm_pv_unhalt,+kvm_pv_eoi,kvm=off \
-m 8192 \
-object memory-backend-ram,size=8192M,id=ram-node0 \
-numa node,nodeid=0,cpus=0-11,memdev=ram-node0 \
-k en-us \
-readconfig /usr/share/qemu-server/pve-q35.cfg \
-device usb-tablet,id=tablet,bus=ehci.0,port=1 \
-device vfio-pci,host=04:00.0,id=hostpci0,bus=ich9-pcie-port-1,addr=0x0 \
-device vfio-pci,host=04:00.1,id=hostpci1,bus=ich9-pcie-port-2,addr=0x0 \
-device usb-host,hostbus=1,hostport=6.1 \
-device usb-host,hostbus=1,hostport=6.2.1 \
-device usb-host,hostbus=1,hostport=6.2.2 \
-device usb-host,hostbus=1,hostport=6.2.3 \
-device usb-host,hostbus=1,hostport=6.2 \
-device usb-host,hostbus=1,hostport=6.3 \
-device usb-host,hostbus=1,hostport=6.4 \
-device usb-host,hostbus=1,hostport=6.5 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
-drive file=/dev/zvol/SSD-pool/vm-110-disk-1,if=none,id=drive-virtio0,cache=writeback,format=raw,aio=threads,detect-zeroes=on \
-device virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,bootindex=100 \
-netdev type=tap,id=net0,ifname=tap110i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown,vhost=on \
-device virtio-net-pci,mac=32:61:36:63:37:64,netdev=net0,bus=pci.0,addr=0x12,id=net0 \
-rtc driftfix=slew,base=localtime \
-machine type=q35 \
-global kvm-pit.lost_tick_policy=discard

VM2:

# sed -e 's/#.*$//' -e '/^$/d' /root/src/madzia.2
/usr/bin/systemd-run \
--scope \
--slice qemu \
--unit 111 \
-p KillMode=none \
-p CPUShares=250000 \
/usr/bin/kvm \
-id 111 \
-chardev socket,id=qmp,path=/var/run/qemu-server/111.qmp,server,nowait \
-mon chardev=qmp,mode=control \
-pidfile /var/run/qemu-server/111.pid \
-daemonize \
-smbios type=1,uuid=55d862f4-d9b9-40ab-9b0a-e1eadf874750 \
-drive if=pflash,format=raw,readonly,file=/usr/share/kvm/OVMF-pure-efi.fd \
-drive if=pflash,format=raw,file=/root/sbin/111-OVMF_VARS-pure-efi.fd \
-name Madzia-PC \
-smp 12,sockets=1,cores=12,maxcpus=12 \
-nodefaults \
-boot menu=on,strict=on,reboot-timeout=1000 \
-vga none \
-nographic \
-no-hpet \
-cpu host,hv_vendor_id=Nvidia43FIX,hv_spinlocks=0x1fff,hv_vapic,hv_time,hv_relaxed,+kvm_pv_unhalt,+kvm_pv_eoi,kvm=off \
-m 8192 \
-object memory-backend-ram,size=8192M,id=ram-node0 \
-numa node,nodeid=0,cpus=0-11,memdev=ram-node0 \
-k en-us \
-readconfig /usr/share/qemu-server/pve-q35.cfg \
-device usb-tablet,id=tablet,bus=ehci.0,port=1 \
-device vfio-pci,host=05:00.0,id=hostpci0,bus=ich9-pcie-port-1,addr=0x0 \
-device vfio-pci,host=05:00.1,id=hostpci1,bus=ich9-pcie-port-2,addr=0x0 \
-device usb-host,hostbus=2,hostport=2.1 \
-device usb-host,hostbus=2,hostport=2.2 \
-device usb-host,hostbus=2,hostport=2.3 \/
-device usb-host,hostbus=2,hostport=2.4 \
-device usb-host,hostbus=2,hostport=2.5 \
-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3 \
-iscsi initiator-name=iqn.1993-08.org.debian:01:1530d013b944 \
-drive file=/dev/zvol/SSD-pool/vm-111-disk-1,if=none,id=drive-virtio0,cache=writeback,format=raw,aio=threads,detect-zeroes=on \
-device virtio-blk-pci,drive=drive-virtio0,id=virtio0,bus=pci.0,addr=0xa,bootindex=100 \
-netdev type=tap,id=net0,ifname=tap111i0,script=/var/lib/qemu-server/pve-bridge,downscript=/var/lib/qemu-server/pve-bridgedown,vhost=on \
-device virtio-net-pci,mac=4E:F0:DD:90:DB:2D,netdev=net0,bus=pci.0,addr=0x12,id=net0 \
-rtc driftfix=slew,base=localtime \
-machine type=q35 \
-global kvm-pit.lost_tick_policy=discard

However, I've tried many invocations of KVM without success.

Here is how I load my modules:


# cat /etc/modprobe.d/iommu_unsafe_interrupts.conf
options vfio_iommu_type1 allow_unsafe_interrupts=1



# cat /etc/modprobe.d/vfio_pci.conf
options vfio_pci disable_vga=1
#install vfio_pci /root/sbin/vfio-pci-override-vga.sh
options vfio-pci ids=10de:13c2,10de:0fbb,10de:11c0,10de:0e0b



# cat /etc/modprobe.d/zfs.conf
options zfs zfs_arc_max=4299967296



# cat /etc/modprobe.d/kvm.conf
options kvm ignore_msrs=1


... I believe grub is set up correctly ...


# sed -e 's/#.*$//' -e '/^$/d' /etc/default/grub
GRUB_DEFAULT=0
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="Proxmox Virtual Environment"
GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=on vfio_iommu_type1.allow_unsafe_interrupts=1 quiet"
GRUB_CMDLINE_LINUX=""
GRUB_DISABLE_OS_PROBER=true
GRUB_DISABLE_RECOVERY="true"
*

...  I believe I have all the correct modules loaded on boot ...


# sed -e 's/#.*$//' -e '/^$/d' /etc/modules
coretemp
it87
vfio
vfio_iommu_type1
vfio_pci
vfio_virqfd


... Here's the Q35 config file ...


# sed -e 's/#.*$//' -e '/^$/d' /usr/share/qemu-server/pve-q35.cfg
[device "ehci"]
  driver = "ich9-usb-ehci1"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1d.7"
[device "uhci-1"]
  driver = "ich9-usb-uhci1"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1d.0"
  masterbus = "ehci.0"
  firstport = "0"
[device "uhci-2"]
  driver = "ich9-usb-uhci2"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1d.1"
  masterbus = "ehci.0"
  firstport = "2"
[device "uhci-3"]
  driver = "ich9-usb-uhci3"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1d.2"
  masterbus = "ehci.0"
  firstport = "4"
[device "ehci-2"]
  driver = "ich9-usb-ehci2"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1a.7"
[device "uhci-4"]
  driver = "ich9-usb-uhci4"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1a.0"
  masterbus = "ehci-2.0"
  firstport = "0"
[device "uhci-5"]
  driver = "ich9-usb-uhci5"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1a.1"
  masterbus = "ehci-2.0"
  firstport = "2"
[device "uhci-6"]
  driver = "ich9-usb-uhci6"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1a.2"
  masterbus = "ehci-2.0"
  firstport = "4"
[device "audio0"]
  driver = "ich9-intel-hda"
  bus = "pcie.0"
  addr = "1b.0"
[device "ich9-pcie-port-1"]
  driver = "ioh3420"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1c.0"
  port = "1"
  chassis = "1"
[device "ich9-pcie-port-2"]
  driver = "ioh3420"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1c.1"
  port = "2"
  chassis = "2"
[device "ich9-pcie-port-3"]
  driver = "ioh3420"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1c.2"
  port = "3"
  chassis = "3"
[device "ich9-pcie-port-4"]
  driver = "ioh3420"
  multifunction = "on"
  bus = "pcie.0"
  addr = "1c.3"
  port = "4"
  chassis = "4"
[device "pcidmi"]
  driver = "i82801b11-bridge"
  bus = "pcie.0"
  addr = "1e.0"
[device "pci.0"]
  driver = "pci-bridge"
  bus = "pcidmi"
  addr = "1.0"
  chassis_nr = "1"
[device "pci.1"]
  driver = "pci-bridge"
  bus = "pcidmi"
  addr = "2.0"
  chassis_nr = "2"
[device "pci.2"]
  driver = "pci-bridge"
  bus = "pcidmi"
  addr = "3.0"
  chassis_nr = "3"

... and plenty of CPU ...


# cat /proc/cpuinfo | grep  -A 4 processor.*": 11"
processor       : 11
vendor_id       : GenuineIntel
cpu family      : 6
model           : 44
model name      : Intel(R) Xeon(R) CPU           X 000  @ 2.93GHz


In case this is really a problem with qemu/kvm, I've also posted on their list.  Hope that's not impolite.

If anyone has any suggestions, I would greatly appreciate it.


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