Re: [PATCH 3/5] x86/ibrs: Add direct access support for MSR_IA32_SPEC_CTRL

[Dave Hansen]

On 01/11/2018 05:32 PM, Ashok Raj wrote:
> +static void save_guest_spec_ctrl(struct vcpu_vmx *vmx)
> +{
> +	if (boot_cpu_has(X86_FEATURE_SPEC_CTRL)) {
> +		vmx->spec_ctrl = spec_ctrl_get();
> +		spec_ctrl_restriction_on();
> +	} else
> +		rmb();
> +}

Does this need to be "ifence()"?  Better yet, do we just need to create
a helper for boot_cpu_has(X86_FEATURE_SPEC_CTRL) that does the barrier?