diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index c589ac832265c47cb37c2b917d2551599713c29f..532791ffcbb92e175ee8c528f87a105e3cb8db62 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4223,6 +4223,11 @@ static int check_rdpmc(struct x86_emulate_ctxt *ctxt)
 	if (enable_vmware_backdoor && is_vmware_backdoor_pmc(rcx))
 		return X86EMUL_CONTINUE;
 
+	/*
+	 * If CR4.PCE is set, the SDM requires CPL=0 or CR0.PE=0.  The CR0.PE
+	 * check however is unnecessary because CPL is always 0 outside
+	 * protected mode.
+	 */
 	if ((!(cr4 & X86_CR4_PCE) && ctxt->ops->cpl(ctxt)) ||
 	    ctxt->ops->check_pmc(ctxt, rcx))
 		return emulate_gp(ctxt, 0);