On 9/23/22 15:32, Gerd Hoffmann wrote: > On Tue, Sep 13, 2022 at 12:50:22PM +0200, Antonio Caggiano wrote: >> From: Dmitry Osipenko <dmitry.osipe...@collabora.com> >> >> Host blobs don't need udmabuf, it's only needed by guest blobs. The host >> blobs are utilized by the Mesa virgl driver when persistent memory mapping >> is needed by a GL buffer, otherwise virgl driver doesn't use blobs. >> Persistent mapping support bumps GL version from 4.3 to 4.5 in guest. >> Relax the udmabuf requirement. > > What about blob=on,virgl=off? > > In that case qemu manages the resources and continued to require > udmabuf.
The udmabuf is used only by the blob resource-creation command in Qemu. I couldn't find when we could hit that udmabuf code path in Qemu because BLOB_MEM_GUEST resource type is used only by crosvm+Venus when crosvm uses a dedicated render-server for virglrenderer. Summarizing: - only BLOB_MEM_GUEST resources require udmabuf - /dev/udmabuf isn't accessible by normal user - udmabuf driver isn't shipped by all of the popular Linux distros, for example Debian doesn't ship it Because of all of the above, I don't think it makes sense to hard-require udmabuf at the start of Qemu. It's much better to fail resource creation dynamically. -- Best regards, Dmitry
