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[92.176.231.205]) by smtp.gmail.com with ESMTPSA id v18-20020a05600c4d9200b004068495910csm17570724wmp.23.2023.11.14.10.06.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Nov 2023 10:06:47 -0800 (PST) From: Javier Martinez Canillas To: Thomas Zimmermann , linux-kernel@vger.kernel.org Cc: Pekka Paalanen , dri-devel@lists.freedesktop.org, Jonathan Corbet , Bilal Elmoussaoui , linux-doc@vger.kernel.org, Maxime Ripard , Gurchetan Singh , VMware Graphics Reviewers , Gerd Hoffmann , Sima Vetter , David Airlie , virtualization@lists.linux-foundation.org, Erico Nunes Subject: Re: [PATCH 0/6] drm: Allow the damage helpers to handle buffer damage In-Reply-To: References: <20231109172449.1599262-1-javierm@redhat.com> <9296c184-22c1-4d71-8b11-2d26f49a5790@suse.de> <87wmuk5mfj.fsf@minerva.mail-host-address-is-not-set> Date: Tue, 14 Nov 2023 19:06:47 +0100 Message-ID: <87ttpo5hvs.fsf@minerva.mail-host-address-is-not-set> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Thomas Zimmermann writes: Hello Thomas, > Hi [...] >>> And why does it flicker? Is there old data stored somewhere? >>> >> >> It flickers because the framebuffer changed and so the damage tracking >> is not used correctly to flush the damaged areas to the backing storage. > > I think I got it from the links in patch 5. In out other drivers, > there's a single backing storage for each plane (for example in the > video memory). Here, there's a backing storage for each buffer. On page Correct, that's what I understood too. > flips, the plane changes its backing storage. Our GEM buffer is up to > date, but the respective backing storage is missing all the intermediate > changes. > > If I'm not mistaken, an entirely different solution would be to > implement a per-plane back storage in these drivers. > I believe so but I'm not sure if that's possible since the virtio-gpu spec defines that the VM should send a VIRTIO_GPU_CMD_RESOURCE_FLUSH to the VMM in the host to do an update and the granularity for that is a framebuffer. For that reason the only solution (other than forcing a full plane update like this patch-set does) is to implement tracking suppor for buffer damage. > Best regards > Thomas > -- Best regards, Javier Martinez Canillas Core Platforms Red Hat