feat: added notice about CR4.VMXE bit

docs/re.md

@@ -95,6 +95,11 @@ static bool vmx_supported(void) {
 
 ### Enabling VMX in CR4
 
+> [!IMPORTANT]
+> Looks like, when virtualization has been activated through the BIOS, the 13th
+> bit of CR4 is **always** set. Thus, setting this bit manually seems to be a
+> no-op.
+
 In order to enter VMX operation, the software (our hypervisor) has to firstly
 enable VMX by setting the 13th bit of the CR4 register to 1. This will of course
 throw an exception if this code is being executed from user-space. That's why