Bug 1005037 - When using “-vga qxl” together with “-display vnc=:5” or “-display sdl” qemu displays pixel garbage
When using “-vga qxl” together with “-display vnc=:5” or “-display sdl” qemu...
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: qemu-kvm (Show other bugs)
Unspecified Unspecified
medium Severity medium
: rc
: ---
Assigned To: Gerd Hoffmann
Virtualization Bugs
Depends On: 948717
Blocks: 1005036
  Show dependency treegraph
Reported: 2013-09-06 01:21 EDT by Gerd Hoffmann
Modified: 2014-10-14 02:50 EDT (History)
23 users (show)

See Also:
Fixed In Version: qemu-kvm-
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: 948717
Last Closed: 2014-10-14 02:50:35 EDT
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
pixel garbage (473.91 KB, image/png)
2013-09-15 22:25 EDT, zhonglinzhang
no flags Details
snapshot of guest (175.42 KB, image/png)
2014-06-20 03:14 EDT, mazhang
no flags Details
screenshot (52.99 KB, image/png)
2014-06-20 03:45 EDT, mazhang
no flags Details

  None (edit)
Description Gerd Hoffmann 2013-09-06 01:21:38 EDT
+++ This bug was initially created as a clone of Bug #948717 +++

qemu-1.4.0-11.fc18.x86_64 from  https://fedoraproject.org/wiki/Virtualization_Preview_Repository


qemu command line:

ionice -c 3 qemu-kvm -enable-kvm -m 2048M -smp 1 -drive file=./Fedora-19-Alpha-TC4-x86_64-netinst-test.iso.qcow2,index=0,media=disk,cache=unsafe -localtime -serial file:/tmp/qemu-Fedora-19-Alpha-TC4-x86_64-netinst-test.iso.qcow2-output.log -name Fedora-19-Alpha-TC4-x86_64-netinst-test.iso.qcow2 -cdrom /local/mfabian/iso/Fedora-19-Alpha-TC4/Fedora-19-Alpha-TC4-x86_64-netinst.iso -boot c -vga qxl -display vnc=:5 -net nic -net user,hostname=Fedora-19-Alpha-TC4-x86_64-netinst-test.iso.qcow2,hostfwd=tcp::5562-:22 -monitor stdio -usb

The above commandline has “-display vnc=:5”, the problem occurs
with “-display sdl” as well though.

The result is pixel garbage, see attached  screen shot.

When using “-vga std” or  “-vga cirrus” instead  of “-vga qxl” it works
fine, no pixel garbage.

--- Additional comment from Cole Robinson on 2013-04-14 21:55:06 CEST ---

I can reproduce with upstream. Grab F19 boot.iso here:


And run:

./x86_64-softmmu/qemu-system-x86_64 -enable-kvm -vga qxl -display sdl -cdrom ~/boot.iso -m 2048

Doing -device qxl works fine though. I also tried an F16 live cd I had hanging around and that worked fine, so maybe it's an F19 driver issue.

Alon, Gerd, thoughts?

--- Additional comment from Cole Robinson on 2013-05-28 01:01:01 CEST ---

Ping, any spice folks want to weigh in on this? Granted qxl->vnc shouldn't be a common setup, but people tend to try it out if hitting graphical issues and wanting to eliminate spice from the equation (for better or worse).

--- Additional comment from Steve Tyler on 2013-07-31 15:33:52 CEST ---

Confirming severe display corruption with the "-vga qxl" option.
With the "-vga std" option, there is no corruption.

By blindly clicking in the upper right corner, pressing the down-arrow four times, and pressing Enter twice, it is possible to power off the VM, if the corrupt display shows parts of the Welcome dialog.

Steps to reproduce:
$ qemu-kvm -m 4096 -cdrom ~/xfr/fedora/F19/Fedora-Live-Desktop-x86_64-19-1.iso -vga qxl

kernel 3.10.3-300.fc19.x86_64

--- Additional comment from Jan Kratochvil on 2013-08-19 20:36:29 CEST ---

/usr/bin/qemu-kvm -m 2048 -cdrom Fedora-19-x86_64-DVD.iso -boot d -vnc :10 -vga qxl

--- Additional comment from Mike FABIAN on 2013-08-31 08:07:40 CEST ---

The problem still exists with Fedora-20-Alpha-TC2-x86_64-netinst.iso
and qemu-1.6.0-5.fc19.x86_64
Comment 2 Gerd Hoffmann 2013-09-12 05:19:02 EDT
patches posted.
Comment 3 zhonglinzhang 2013-09-13 05:36:19 EDT
Can not reproduce this issue:

host kernel: 2.6.32-417.el6.x86_64

Command line as follows:
ionice -c 3 /usr/libexec/qemu-kvm -M pc -nodefaults  -cpu SandyBridge -enable-kvm -m 4G -smp 2,sockets=1,cores=2,threads=1  -name test -rtc base=localtime,clock=host,driftfix=slew  -k en-us  -boot menu=on  -vga qxl -vnc :5 -monitor stdio ...

host kernel: 3.9.9-201.fc18.x86_64

Command line as follows:
ionice -c 3 qemu-kvm -enable-kvm -m 2048M -smp 1 -drive file=RHEL_65_64.qcow2,media=disk,cache=unsafe  -localtime -boot c -vga qxl  -display sdl -monitor stdio

Actual Results:
Only show pixel garbage before login screen, but very fast passed. the same result with “-vga std” or “-vga cirrus”.
Comment 4 Gerd Hoffmann 2013-09-13 06:56:18 EDT
Re #3: RHEL-6 doesn't trigger it, try RHEL-7 or Fedora-19 as guest.
Comment 6 zhonglinzhang 2013-09-15 22:25:28 EDT
Created attachment 798084 [details]
pixel garbage
Comment 7 zhonglinzhang 2013-09-15 22:28:17 EDT
Reproduce with host kernel 2.6.32-417.el6.x86_64
guest rhel7.0

The result is pixel garbage, see attached "attachment 798084 [details]"
Comment 11 mazhang 2014-06-20 03:13:19 EDT
Reproduce this bug on qemu-kvm-



/usr/libexec/qemu-kvm \
-M pc \
-cpu SandyBridge \
-m 4G \
-smp 4,sockets=2,cores=2,threads=1,maxcpus=160 \
-enable-kvm \
-name rhel6.6 \
-uuid 990ea161-6b67-47b2-b803-19fb01d30d12 \
-smbios type=1,manufacturer='Red Hat',product='RHEV Hypervisor',version=el6,serial=koTUXQrb,uuid=feebc8fd-f8b0-4e75-abc3-e63fcdb67170 \
-k en-us \
-rtc base=localtime,clock=host,driftfix=slew \
-nodefaults \
-monitor stdio \
-qmp tcp:0:6666,server,nowait \
-boot menu=on,strict=on \
-bios /usr/share/seabios/bios.bin \
-chardev socket,id=seabios,path=/tmp/seabios,server,nowait \
-device isa-debugcon,chardev=seabios,iobase=0x402 \
-monitor unix:/tmp/guest-sock,server,nowait \
-vga qxl \
-vnc :0 \
-drive file=/home/rhel7-64.qcow2,if=none,id=drive-virtio-disk0,format=qcow2,cache=none,werror=stop,rerror=stop,aio=threads \
-device virtio-blk-pci,scsi=off,bus=pci.0,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 \

Display pixel garbage.
Comment 12 mazhang 2014-06-20 03:14:08 EDT
Created attachment 910666 [details]
snapshot of guest
Comment 13 mazhang 2014-06-20 03:44:44 EDT
Test this bug on qemu-kvm-, Guest hang during boot, and display black, will attach the screenshot.
Comment 14 mazhang 2014-06-20 03:45:25 EDT
Created attachment 910670 [details]
Comment 15 mazhang 2014-06-20 03:59:06 EDT
Hi Gerd,

1. Try reproduce this bug with "qxl+vnc" as bug 948717#c2 and 948717#c4 mentioned, since "-display" option has been removed from qemu-kvm, Please help check comment#11 and comment#13, if any problem please correct me.

2. Does qxl+vnc support officially, we need test this scenario in rhel6.6?

Comment 16 Gerd Hoffmann 2014-06-20 04:31:59 EDT
Screenshot shows two text console lines.  No pixel garbage -> bug is fixed.

Guest not booting is most likely a separate (guest) bug.
Does that happen with vnc only or is spice affected too?
Comment 17 mazhang 2014-06-20 04:42:46 EDT
Just have a try, spice+qxl works well.
Comment 18 mazhang 2014-06-23 02:41:10 EDT
1. According to comment#11 comment#13 and comment#16 setting this bug to verified.
2. File a new bug 1112078 against guest desktop booting fails.
Comment 19 errata-xmlrpc 2014-10-14 02:50:35 EDT
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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