x86: Add a cpuid command

It is useful to obtain the results of cpuid queries, so add a command
for this.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/x86/Makefile

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0+
 
 obj-$(CONFIG_CMD_CBSYSINFO) += cbsysinfo.o
-obj-y += mtrr.o
+obj-y += cpuid.o mtrr.o
 obj-$(CONFIG_CMD_EXCEPTION) += exception.o
 obj-$(CONFIG_USE_HOB) += hob.o
 obj-$(CONFIG_HAVE_FSP) += fsp.o

cmd/x86/cpuid.c

@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * The 'cpuid' command provides access to the CPU's cpuid information
+ *
+ * Copyright 2024 Google, LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#include <command.h>
+#include <vsprintf.h>
+#include <asm/cpu.h>
+
+static int do_cpuid(struct cmd_tbl *cmdtp, int flag, int argc,
+		    char *const argv[])
+{
+	struct cpuid_result res;
+	ulong op;
+
+	if (argc < 2)
+		return CMD_RET_USAGE;
+
+	op = hextoul(argv[1], NULL);
+	res = cpuid(op);
+	printf("eax %08x\n", res.eax);
+	printf("ebx %08x\n", res.ebx);
+	printf("ecx %08x\n", res.ecx);
+	printf("edx %08x\n", res.edx);
+
+	return 0;
+}
+
+U_BOOT_LONGHELP(cpuid, "Show CPU Identification information");
+
+U_BOOT_CMD(
+	cpuid,	2,	1,	do_cpuid,
+	"cpuid <op>", cpuid_help_text
+);