KVM: x86: Ensure all logical CPUs have consistent reserved cr4 bits

Check the current CPU's reserved cr4 bits against the mask calculated
for the boot CPU to ensure consistent behavior across all CPUs.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -9461,6 +9461,13 @@ void kvm_arch_hardware_unsetup(void)
 
 int kvm_arch_check_processor_compat(void)
 {
+	struct cpuinfo_x86 *c = &cpu_data(smp_processor_id());
+
+	WARN_ON(!irqs_disabled());
+
+	if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits)
+		return -EIO;
+
 	return kvm_x86_ops->check_processor_compatibility();
 }