x86/nmi: Rate limit unknown NMI messages

On some AMD machines, unknown NMI messages were printed on the console
continuously when using perf command with IBS.  It was reported that it
can slow down the kernel. Ratelimit the unknown NMI messages.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Ravi Bangoria <ravi.bangoria@amd.com>
Acked-by: Guilherme Amadio <amadio@gentoo.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20231209015211.357983-1-namhyung@kernel.org

arch/x86/kernel/nmi.c

@@ -303,13 +303,13 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 
 	__this_cpu_add(nmi_stats.unknown, 1);
 
-	pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
-		 reason, smp_processor_id());
+	pr_emerg_ratelimited("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
+			     reason, smp_processor_id());
 
 	if (unknown_nmi_panic || panic_on_unrecovered_nmi)
 		nmi_panic(regs, "NMI: Not continuing");
 
-	pr_emerg("Dazed and confused, but trying to continue\n");
+	pr_emerg_ratelimited("Dazed and confused, but trying to continue\n");
 }
 NOKPROBE_SYMBOL(unknown_nmi_error);