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[Bug 1851972] Re: pc-q35-4.1 and AMD Navi 5700/XT incompatible

From: Marshall Porter
Subject: [Bug 1851972] Re: pc-q35-4.1 and AMD Navi 5700/XT incompatible
Date: Thu, 09 Jan 2020 06:37:45 -0000

Hi Philippe, thanks for replying.

The 'kernel_irqchip' parameter is a bit confusing to me. It looks like
the documentation was updated from it defaulted to 'off' as a -machine
parameter, to now it will default to 'on' as an -accel parameter.

This bug described how the value for 'default_kernel_irqchip_split'
parameter had been changed to 'true' in Q35 version 4.0, but then set
back to 'false' after discovering that it caused issues for Nvidia gpu
passthrough and other things:

However, my problems with the AMD gpu passthrough are present when
switching between Q35 3.0 (which does work) and 3.1 (which does not
work), both of which would still have 'default_kernel_irqchip_split' set
to false.. so it does not seem to me to be related to 'kernel_irqchip'.

Q35 version 3.1 did introduce many other changes:

static void pc_q35_3_1_machine_options(MachineClass *m)
    pcmc->do_not_add_smb_acpi = true;
    m->smbus_no_migration_support = true;
    m->alias = NULL;
    pcmc->pvh_enabled = false;

GlobalProperty hw_compat_3_1[] = {
    { "pcie-root-port", "x-speed", "2_5" },
    { "pcie-root-port", "x-width", "1" },

I thought maybe those could cause the AMD Navi gpu problems, but I am
not that knowledgeable about these settings.

Also I do not have the AMD Navi gpu conveniently available anymore to

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  pc-q35-4.1 and AMD Navi 5700/XT incompatible

Status in QEMU:

Bug description:

  I am not sure if this qualifies as a "bug"; it is be more of an
  unknown issue with default settings. However, since the default value
  of q35 default_kernel_irqchip_split was changed seemingly due to
  similar user feedback, I thought this was important to share..

  AMD Navi 5700/XT vfio-pci passthrough seems incompatible with
  one/multiple settings in pc-q35-3.1 and higher. The workaround for me
  is that pc-q35-3.0 still works fine passing through the GPU and
  official drivers can load/install fine.

  The default/generic GPU drivers in a Fedora 30 or Windows 1903 guest
  do work; the monitor displays the desktop in a 800x600 resolution and
  things are rendered fine.. so the basic functionality of the card
  seems fine with pc-q35-4.1.

  But attempting to use the official open source AMD driver with the
  card resulted in a hung kernel for the Fedora 30 guest.. and a BSOD on
  the Windows 1903 guest immediately during driver install.

  I do not see any errors in Qemu command output.. did not investigate
  other logs or KVM etc, because I am not sure what to look for or how
  to go about it. Also not sure which combination of the latest q35
  default settings are valid combinations to try either, because it
  seems that multiple things have changed related to pcie-root-port
  defaults and other machine options. I am happy to run tests and
  provide feedback if that helps identify the issue.

  I am using "Linux arch 5.4.0-rc6-mainline" kernel on ArchLinux host
  with AMD Navi reset pci quirk patch applied.

  My working Qemu command line is this:

  QEMU_PA_SERVER=/run/user/1000/pulse/native \
  /usr/bin/qemu-system-x86_64 \
  -name windows \
  -m 16g \
  -accel kvm \
  -machine pc-q35-3.0,accel=kvm,pflash0=ovmf0,pflash1=ovmf1 \
node-name=ovmf0,driver=file,filename=/virt/qemu/roms/OVMF_CODE.fd,read-only=on \
node-name=ovmf1,driver=file,filename=/virt/qemu/machines/windows/OVMF_VARS.fd \
  -boot menu=on \
  -global kvm-pit.lost_tick_policy=discard \
  -no-hpet \
  -rtc base=utc,clock=host,driftfix=slew \
  -smp sockets=1,cores=4,threads=1 \
  -nodefaults \
  -netdev bridge,br=br0,id=net0 \
  -device virtio-net-pci,netdev=net0,addr=19.0,mac=52:54:00:12:34:77 \
  -device virtio-scsi-pci \
  -device scsi-hd,drive=disk0,rotation_rate=1 \
  -device scsi-hd,drive=disk1,rotation_rate=1 \
  -device ich9-intel-hda,addr=1b.0 \
  -device hda-output \
  -monitor stdio \
  -display none \
  -vga none \
  -device pcie-root-port,id=pcierp1,chassis=2,slot=2,addr=1c.1,disable-acs=on \
  -device x3130-upstream,bus=pcierp0,id=pcieu0 \
  -device xio3130-downstream,bus=pcieu0,id=pcied0,chassis=11,slot=11 \
  -device vfio-pci,host=03:00.0,bus=pcied0,addr=00.0,multifunction=on \
  -device vfio-pci,host=03:00.1,bus=pcied0,addr=00.1 \
  -device qemu-xhci,addr=1d.0 \
  -device usb-host,vendorid=0x258a,productid=0x0001 \
  -device usb-host,vendorid=0x1bcf,productid=0x0005 ;

  Thank you!

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