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.