Hi Dmitry, > > On 9/27/22 11:32, Gerd Hoffmann wrote: > > On Mon, Sep 26, 2022 at 09:32:40PM +0300, Dmitry Osipenko wrote: > >> 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. > > > > Recent enough linux guest driver will use BLOB_MEM_GUEST resources > > with blob=on + virgl=off > > I reproduced this case today using "-device > virtio-gpu-device,blob=true". You're right, it doesn't work without udmabuf. > > [ 8.369306] virtio_gpu_dequeue_ctrl_func: 90 callbacks suppressed > [ 8.369311] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1200 (command 0x105) > [ 8.371848] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1205 (command 0x104) > [ 8.373085] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1200 (command 0x105) > [ 8.376273] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1205 (command 0x104) > [ 8.416972] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1200 (command 0x105) > [ 8.418841] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response > 0x1205 (command 0x104) > > I see now why you're wanting to keep the udmabuf requirement for > blob=on,virgl=off. > > > >> - /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 > > > > That's why blob resources are off by default. > > > >> 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. > > > > Disagree. When virgl/venus is enabled, then yes, qemu would let > > virglrenderer manage resources and I'm ok with whatever requirements > > virglrenderer has. When qemu manages resources by itself udmabuf is > > a hard requirement for blob support though. > > Let's try to relax the udmabuf requirement only for blob=on,virgl=on. > I'll update this patch. [Kasireddy, Vivek] In addition to what Gerd mentioned and what you have discovered, I wanted to briefly add that we use Udmabuf/Guest Blobs for Headless GPU passthrough use-cases (blob=on and virgl=off). Here are some more details about our use-case: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9592#note_851314
Thanks, Vivek > > Thank you very much for the review! > > -- > Best regards, > Dmitry >
