On 2/23/23 13:15, Michael Kelley (LINUX) wrote: > Or statically set a default stub function for is_private_mmio() that returns "false". > Then there's no need to check for NULL, and only platforms that want to use it > have to code anything. Several other entries in x86_platform have such defaults. Yeah, that's what I was thinking too, like 'x86_op_int_noop': > struct x86_platform_ops x86_platform __ro_after_init = { > .calibrate_cpu = native_calibrate_cpu_early, > .calibrate_tsc = native_calibrate_tsc, ... > .hyper.pin_vcpu = x86_op_int_noop, It's kinda silly to do an indirect call to a two-instruction function, but this is a pretty slow path.