[Qemu-devel] [Bug 1843151] Re: Regression: QEMU 4.1.0 qxl and KMS resoluiton only 4x10

[James Harvey <jamespharvey20@gmail.com>]

Finding a minimal case did shed some light on this.

Using QEMU's native graphics window, this works fine:

$ /usr/bin/qemu-system-x86_64 \
   -m 1G \
   -blockdev raw,node-name=install_iso,read-only=on,file.driver=file,file.filename=/mnt/losable/ISOs/archlinux-2019.09.01-x86_64.iso \
   -device ide-cd,drive=install_iso,bus=ide.0,bootindex=0

But, introducing spice reproduces the problem:

$ /usr/bin/qemu-system-x86_64 \
   -m 1G \
   -blockdev raw,node-name=install_iso,read-only=on,file.driver=file,file.filename=/mnt/losable/ISOs/archlinux-2019.09.01-x86_64.iso \
   -spice unix,addr=/tmp/spice.qxl.sock,disable-ticketing \
   -device ide-cd,drive=install_iso,bus=ide.0,bootindex=0 \
   -vga qxl

$ remote-viewer "spice+unix:///tmp/spice.qxl.sock"

I've been running remote-viewer (from virt-viewer package) since around
March 13, version 8.0 since then.  It's only when upgrading QEMU from
4.0.0 to 4.1.0 that introduces the problem.

Running remote-viewer this way also shows that it outputs these, right
when KMS changes resolution:

(remote-viewer:15090): GLib-GObject-WARNING **: 23:56:03.914: value "64"
of type 'gint' is invalid or out of range for property 'desktop-width'
of type 'gint'

(remote-viewer:15090): GLib-GObject-WARNING **: 23:56:03.915: value "64"
of type 'gint' is invalid or out of range for property 'desktop-height'
of type 'gint'

When downgrading to QEMU 4.0.0, remote-viewer STILL outputs these lines
regarding desktop-width and height, when KMS changes resolution.

In case it helps, below are spice-debug logs from remote-viewer.  I've
included the whole log, but also added a bunch of spacing and a header
showing the second worth of output correlating with the KMS resolution
change.

QEMU 4.0.0 without the bug: http://ix.io/1USn

QEMU 4.1.0 with the bug: http://ix.io/1USo

So, it's always possible the fix might need to be in remote-viewer, but
at minimum, the case it would need to handle properly wasn't being given
to it until QEMU 4.1.0.

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https://bugs.launchpad.net/bugs/1843151

Title:
  Regression: QEMU 4.1.0 qxl and KMS resoluiton only 4x10

Status in QEMU:
  New

Bug description:
  Host is Arch Linux.  linux 5.2.13, qemu 4.1.0.  virt-viewer 8.0.

  Guest is Arch Linux Sept 2019 ISO.  linux 5.2.11.

  Have replicated this both on a system using amdgpu and one using
  integrated ASPEED graphics.

  Downgrading from 4.1.0 to 4.0.0 works as usual, see:
  https://www.youtube.com/watch?v=NyMdcYwOCvY

  Going back to 4.1.0 reproduces, see:
  https://www.youtube.com/watch?v=H3nGG2Mk6i0

  4.1.0 displays fine until KMS kicks in.

  Using 4.1.0 with virtio-vga doesn't cause this.

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