On 2024-02-26 16:58, Christian König wrote: > Am 23.02.24 um 17:43 schrieb Michel Dänzer: >> On 2024-02-23 11:04, Michel Dänzer wrote: >>> On 2024-02-23 10:34, Christian König wrote: >>>> Am 23.02.24 um 09:11 schrieb Michel Dänzer: >>>>> On 2024-02-23 08:06, Christian König wrote: >>>>>> Am 22.02.24 um 18:28 schrieb Michel Dänzer: >>>>>>> From: Michel Dänzer <mdaen...@redhat.com> >>>>>>> >>>>>>> Pinning the BO storage to VRAM for scanout would make it inaccessible >>>>>>> to non-P2P dma-buf importers. >>>>>> Thinking more about it I don't think we can do this. >>>>>> >>>>>> Using the BO in a ping/pong fashion for scanout and DMA-buf is actually >>>>>> valid, you just can't do both at the same time. >>>>>> >>>>>> And if I'm not completely mistaken we actually have use cases for this >>>>>> at the moment, >>>>> Those use cases don't have P2P & CONFIG_DMABUF_MOVE_NOTIFY? >>>> Nope, we are basically talking about unit tests and examples for inter >>>> device operations. >>> Sounds like the "no user-space regressions" rule might not apply then. >> To clarify what I mean by that: >> >> "We can't fix this issue, because it would break some unit tests and >> examples" is similar to saying "We can't fix this KMS bug, because there are >> IGT tests expecting the buggy behaviour". In practice, the latter do get >> fixed, along with the IGT tests. > > The problem here is that this is not a bug, but intentional behavior. > Exporting BOs and using them in scanout in a ping/pong fashion is perfectly > valid.
The problem with the status quo is that it requires amdgpu-specific knowledge and worst-case pessimization in user space. > We have use cases which depend on this behavior and I'm not going to break > those to fix your use case. It's not "my" use case, it's a Wayland compositor trying to make use of BO sharing and scanout without always pessimizing for the worst case. That's surely more of a real-world use case than unit tests and examples. -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and Xwayland developer
