Support mapping virgl blobs to a fixed location of a hostmem memory
region using new virglrenderer MAP_FIXED API.
This new feature closes multiple problems for virtio-gpu on QEMU:
- Having dedicated memory region for each mapped blob works notoriously
slow due to QEMU's memory region software design built around RCU that
isn't optimized for frequent removal of the regions
- KVM isn't optimized for a frequent slot changes too
- QEMU/KVM has a limit for a total number of created memory regions,
crashing QEMU when limit is reached
This patch makes virtio-gpu-gl to pre-create a single anonymous memory
region covering whole hostmem area to which blobs will be mapped using
the MAP_FIXED API.
Not all virgl resources will support mapping at a fixed memory address. For
them, we will continue to create individual nested memory sub-regions. In
particular, vrend resources may not have MAP_FIXED capability.
Venus and DRM native contexts will largely benefit from the MAP_FIXED
feature in terms of performance and stability improvement.
Tested-by: Yiwei Zhang <zzyiwei@gmail.com>
Reviewed-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Message-ID: <20260303151422.977399-19-dmitry.osipenko@collabora.com>
Message-ID: <20260304165043.1437519-21-alex.bennee@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
4eb0aace85