Re: [PATCH v7 07/10] x86/vmscape: Use static_call() for predictor flush

[Peter Zijlstra]

On Thu, Mar 19, 2026 at 08:41:54AM -0700, Pawan Gupta wrote:
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 68e2df3e3bf5..b75eda114503 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -144,6 +144,17 @@ EXPORT_SYMBOL_GPL(cpu_buf_idle_clear);
>   */
>  DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
>  
> +/*
> + * Controls CPU Fill buffer clear before VMenter. This is a subset of
> + * X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only
> + * mitigation is required.
> + */
> +DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
> +EXPORT_SYMBOL_GPL(cpu_buf_vm_clear);
> +
> +DEFINE_STATIC_CALL_NULL(vmscape_predictor_flush, write_ibpb);
> +EXPORT_STATIC_CALL_GPL(vmscape_predictor_flush);

Does that want to be:

EXPORT_STATIC_CALL_TRAMP_GPL(vmscape_predictor_flush);

The distinction being that if you only export the trampoline, modules
can do the static_call() thing, but cannot do static_call_update().