Re: [PATCH] x86/retpoline: Fill RSB on context switch for affected CPUs

[Andi Kleen]

> +	if ((!boot_cpu_has(X86_FEATURE_PTI) &&
> +	     !boot_cpu_has(X86_FEATURE_SMEP)) || is_skylake_era()) {
> +		setup_force_cpu_cap(X86_FEATURE_RSB_CTXSW);
> +		pr_info("Filling RSB on context switch\n");

We need to do more things for Skylake (like idle and interrupt fill
and possibly deep call cahin), so I don't think it makes sense to

- have an individual flag for each of these. It can be just a single
flag that enables all of this for Skylake

- print something for each of them. that will just be very noisy
without any useful benefit to the user.

-Andi