diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index c1feb62faac4..d754fd0c8674 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -373,8 +373,11 @@ static const struct kvm_vmx_segment_field {
 u64 host_efer;
 
 /*
- * Keep MSR_STAR at the end, as setup_msrs() will try to optimize it
- * away by decrementing the array size.
+ * Though SYSCALL is only supported in 64-bit mode on Intel CPUs, kvm
+ * will emulate SYSCALL in legacy mode if the vendor string in guest
+ * CPUID.0:{EBX,ECX,EDX} is "AuthenticAMD" or "AMDisbetter!" To
+ * support this emulation, IA32_STAR must always be included in
+ * vmx_msr_index[], even in i386 builds.
  */
 const u32 vmx_msr_index[] = {
 #ifdef CONFIG_X86_64