Well, it shouldn’t. Both C and Rust can achieve the same performance. There’s also no overhead for calling Rust from C or vice versa. Theoretically, some detail-optimizations look less horrid in C, but on the other hand, writing parallel code is significantly easier in Rust. Graphics drivers tend to be all about parallelism, although I can’t say how relevant it actually is in this case.

Having said that, it is likely that the initial versions of this new driver will have worse performance, until the code base matures more.