linux-kernel - Re: [BUG][v6.9-rc6] Deadlock with: Revert "drm/qxl: simplify qxl_fence

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Date: Tue, 7 May 2024 18:46:41 +0300 (EEST)
From: Timo Lindfors <timo.lindfors@....fi>
To: Gerd Hoffmann <kraxel@...hat.com>
cc: Timo Lindfors <timo.lindfors@....fi>, David Airlie <airlied@...hat.com>, 
    Linus Torvalds <torvalds@...ux-foundation.org>, 
    Maxime Ripard <mripard@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
    LKML <linux-kernel@...r.kernel.org>, 
    Alex Constantino <dreaming.about.electric.sheep@...il.com>, 
    Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
    Thomas Zimmermann <tzimmermann@...e.de>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [BUG][v6.9-rc6] Deadlock with: Revert "drm/qxl: simplify
 qxl_fence_wait"

On Tue, 7 May 2024, Gerd Hoffmann wrote:
> Worth trying: use vnc.  The qemu vnc server will skip updates when the
> network pipeline is full.  That throttles the frame rate, but also
> reduces the display update latency.

With Debian 12 it seems that the virtio + vnc + firefox combination 
results in a black firefox window. Adding MOZ_ENABLE_WAYLAND=1 makes
the browser visible but I still see the constant redraw behavior when scrolling.

The qxl + spice + firefox combination scrolls smoothly even if I force 
firefox to use wayland. I suppose I could write a more synthetic test if
it would be useful? With systemtap I can trace what happens during a single
scroll event.

> In general the trend seems to be to move to in-guest remote desktop
> solutions.  Do NOT make VMs a special case with a special solution,
> instead handle VMs like bare metal.  Commercial solutions exist for a
> while, some of them are doing hardware-assisted video encoding to send
> the display as video stream to the remote end.  gnome+rdp is a new
> player here, clearly worth a try.

Yes this makes sense. I'm definitely not trying to stick to a particular 
technology but instead try to find the best FOSS solution for the use case 
of hosting linux desktops on a server.

-Timo