A Phoronix report published today highlights significant performance regressions affecting AMD RDNA3 and RDNA4 graphics cards when running the Linux 6.19 kernel. Comprehensive end-of-year benchmarking for these newer architectures was cut short due to a "show-stopping bug" encountered during testing. Despite the issues with current-generation hardware, testing proceeded for older AMD GCN and RDNA series GPUs on Linux 6.19 and Mesa 26.0-devel. The report also noted that Linux 6.19 now defaults GCN 1.0/1.1 graphics cards to utilize the AMDGPU kernel driver. The identified regression points to a critical performance problem impacting AMD's latest GPU generations on the newest kernel.