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Tue, 7 May 2024 10:21:52 +0000 (UTC) Received: by sirius.home.kraxel.org (Postfix, from userid 1000) id D822D1800D4F; Tue, 7 May 2024 12:21:50 +0200 (CEST) Date: Tue, 7 May 2024 12:21:50 +0200 From: Gerd Hoffmann To: Timo Lindfors Cc: David Airlie , Linus Torvalds , Maxime Ripard , Steven Rostedt , LKML , Alex Constantino , Maarten Lankhorst , Thomas Zimmermann , Daniel Vetter Subject: Re: [BUG][v6.9-rc6] Deadlock with: Revert "drm/qxl: simplify qxl_fence_wait" Message-ID: References: <20240502081641.457aa25f@gandalf.local.home> <20240504043957.417aa98c@rorschach.local.home> <20240506-cuddly-elated-agouti-be981d@houat> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 On Tue, May 07, 2024 at 09:38:56AM GMT, Timo Lindfors wrote: > On Tue, 7 May 2024, David Airlie wrote: > > I expec this will reintroduce the other problems that caused this > > change in the first place, but I think this should at least bring us > > back to regression equilibrium. I can't recommend anyone use qxl hw > > over virtio-gpu hw in their VMs, since virtio-gpu is actually hw > > designed for virt. Well, qxl was designed for virt too, but almost two decades ago with 2d acceleration. And alot of complexity, trying to move 2d-accel rendering from the VM guest to the spice client. That complexity still bites us today as this issue shows. With desktop rendering moving to 3d acceleration all that 2d accel stuff became mostly useless though, so you have the downsides of the complexity without any upsides. There have been plans to add 3d-acceleration support to qxl, but they never took off and with virtio-gpu having taken that role meanwhile the idea is dead now. I second the recommendation to avoid qxl. > I would love to switch to virtio. It works ok for local virtual machines but > I have many users who are using Linux desktops hosted on a powerful server > where it is more difficult. With spice and qxl scrolling in a web browser is > smooth, with spice and virtio it seems like larger parts are getting fully > redrawn (and resent over network?). Hmm, I'd expect behavior being quite simliar for stdvga, qxl and virtio-gpu when running a wayland desktop remotely. When running on X11 without 3d acceleration it could be that scroll ops are actually sent as 2d accel blits on qxl, explaining the difference you are seeing. > Now that new gnome is going to come with RDP support I'm also > considering switching to that. Any tips would be appreciated. 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. 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. take care, Gerd