Re: [PATCH v4 02/19] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs_config

[Chao Gao]

>diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
>index f1348b140e7c..e38545d0dd17 100644
>--- a/arch/x86/kvm/vmx/vmx.c
>+++ b/arch/x86/kvm/vmx/vmx.c
>@@ -2634,12 +2634,15 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> 		{ VM_ENTRY_LOAD_IA32_EFER,		VM_EXIT_LOAD_IA32_EFER },
> 		{ VM_ENTRY_LOAD_BNDCFGS,		VM_EXIT_CLEAR_BNDCFGS },
> 		{ VM_ENTRY_LOAD_IA32_RTIT_CTL,		VM_EXIT_CLEAR_IA32_RTIT_CTL },
>+		{ VM_ENTRY_LOAD_IA32_FRED,		VM_EXIT_ACTIVATE_SECONDARY_CONTROLS },

This line should be removed. It enforces that "Activate secondary controls"
is supported iff FRED is supported, which isn't true.

Bit 3 of 2nd VM-exit controls is "Prematurely busy shadow stack". Some CPUs
support it, but not FRED.