x86: use X86_FEATURE_NOPL in alternatives

Use X86_FEATURE_NOPL to determine if it is safe to use P6 NOPs in
alternatives.  Also, replace table and loop with simple if statement.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/alternative.c

@@ -145,35 +145,25 @@ static const unsigned char *const p6_nops[ASM_NOP_MAX+1] = {
 extern char __vsyscall_0;
 const unsigned char *const *find_nop_table(void)
 {
-	return boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
-	       boot_cpu_data.x86 < 6 ? k8_nops : p6_nops;
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
+	    boot_cpu_has(X86_FEATURE_NOPL))
+		return p6_nops;
+	else
+		return k8_nops;
 }
 
 #else /* CONFIG_X86_64 */
 
-static const struct nop {
-	int cpuid;
-	const unsigned char *const *noptable;
-} noptypes[] = {
-	{ X86_FEATURE_K8, k8_nops },
-	{ X86_FEATURE_K7, k7_nops },
-	{ X86_FEATURE_P4, p6_nops },
-	{ X86_FEATURE_P3, p6_nops },
-	{ -1, NULL }
-};
-
 const unsigned char *const *find_nop_table(void)
 {
-	const unsigned char *const *noptable = intel_nops;
-	int i;
-
-	for (i = 0; noptypes[i].cpuid >= 0; i++) {
-		if (boot_cpu_has(noptypes[i].cpuid)) {
-			noptable = noptypes[i].noptable;
-			break;
-		}
-	}
-	return noptable;
+	if (boot_cpu_has(X86_FEATURE_K8))
+		return k8_nops;
+	else if (boot_cpu_has(X86_FEATURE_K7))
+		return k7_nops;
+	else if (boot_cpu_has(X86_FEATURE_NOPL))
+		return p6_nops;
+	else
+		return intel_nops;
 }
 
 #endif /* CONFIG_X86_64 */