Public bug reported:

Problem summary:
----------------
System is a Raspberry Pi 4 Model B Rev 1.4 (8Gb)

While you are connected to a gnome-remote-desktop session in Wayland
(using either RDP or VNC backends) the system log is populated with
these kind of messages several times per second:

...
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 4194304 
bytes), total 32768 (slots), used 14 (slots)
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 4194304 
bytes), total 32768 (slots), used 106 (slots)
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 8294400 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 8294400 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 8294400 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 8294400 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 1933312 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 4194304 
bytes), total 32768 (slots), used 14 (slots)
jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 4194304 
bytes), total 32768 (slots), used 106 (slots)
jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 8294400 
bytes), total 32768 (slots), used 2 (slots)
jun 08 10:13:13 fpgrpi kernel: swiotlb_tbl_map_single: 82 callbacks suppressed
...

The gnome-remote-desktop session works as expected but performance is
degraded.

These messages stops when you disconnect to gnome-remote-desktop
session.

While you are connected to a gnome-remote-desktop session under X11
there are no messages at all and performance is better. So it seems to
be a Wayland only problem.

How to reproduce:
-----------------
Connect to a gnome-remote-session under Wayland (it doesn't care if you connect 
to RDP or VNC backend). These messages will start to populate system log 
immediately. 

Aditional info:
---------------
# lsb_release -rd
Description:    Ubuntu 22.04 LTS
Release:        22.04

#uname -a
Linux fpgrpi 5.15.0-1011-raspi #13-Ubuntu SMP PREEMPT Thu Jun 2 11:44:34 UTC 
2022 aarch64 aarch64 aarch64 GNU/Linux

#apt-cache policy gnome-remote-desktop
gnome-remote-desktop:
  Instalados: 42.1.1-0ubuntu1
  Candidato:  42.1.1-0ubuntu1
  Tabla de versión:
 *** 42.1.1-0ubuntu1 500
        500 http://ports.ubuntu.com/ubuntu-ports jammy-updates/main arm64 
Packages
        100 /var/lib/dpkg/status

** Affects: linux-raspi (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-raspi in Ubuntu.
https://bugs.launchpad.net/bugs/1978051

Title:
  "kernel: vc4-drm gpu: swiotlb buffer is full" messages when connected
  to a gnome-remote-desktop session in wayland

Status in linux-raspi package in Ubuntu:
  New

Bug description:
  Problem summary:
  ----------------
  System is a Raspberry Pi 4 Model B Rev 1.4 (8Gb)

  While you are connected to a gnome-remote-desktop session in Wayland
  (using either RDP or VNC backends) the system log is populated with
  these kind of messages several times per second:

  ...
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
4194304 bytes), total 32768 (slots), used 14 (slots)
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
4194304 bytes), total 32768 (slots), used 106 (slots)
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
8294400 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
8294400 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
8294400 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:08 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
8294400 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
1933312 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
4194304 bytes), total 32768 (slots), used 14 (slots)
  jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
4194304 bytes), total 32768 (slots), used 106 (slots)
  jun 08 10:13:09 fpgrpi kernel: vc4-drm gpu: swiotlb buffer is full (sz: 
8294400 bytes), total 32768 (slots), used 2 (slots)
  jun 08 10:13:13 fpgrpi kernel: swiotlb_tbl_map_single: 82 callbacks suppressed
  ...

  The gnome-remote-desktop session works as expected but performance is
  degraded.

  These messages stops when you disconnect to gnome-remote-desktop
  session.

  While you are connected to a gnome-remote-desktop session under X11
  there are no messages at all and performance is better. So it seems to
  be a Wayland only problem.

  How to reproduce:
  -----------------
  Connect to a gnome-remote-session under Wayland (it doesn't care if you 
connect to RDP or VNC backend). These messages will start to populate system 
log immediately. 

  Aditional info:
  ---------------
  # lsb_release -rd
  Description:  Ubuntu 22.04 LTS
  Release:      22.04

  #uname -a
  Linux fpgrpi 5.15.0-1011-raspi #13-Ubuntu SMP PREEMPT Thu Jun 2 11:44:34 UTC 
2022 aarch64 aarch64 aarch64 GNU/Linux

  #apt-cache policy gnome-remote-desktop
  gnome-remote-desktop:
    Instalados: 42.1.1-0ubuntu1
    Candidato:  42.1.1-0ubuntu1
    Tabla de versión:
   *** 42.1.1-0ubuntu1 500
          500 http://ports.ubuntu.com/ubuntu-ports jammy-updates/main arm64 
Packages
          100 /var/lib/dpkg/status

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-raspi/+bug/1978051/+subscriptions


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