[ACPI] check "maxcpus=N" early -- same as NR_CPUS check.

http://bugzilla.kernel.org/show_bug.cgi?id=2317

When the BIOS enumerates physical processors before logical,
maxcpus=N/2 will now effectively disable HT.

This can be verified by boot messages warning that HT is off:
eg. "maxcpus=2" on a 2xHT system:

Total of 2 processors activated (11141.12 BogoMIPS).
WARNING: No sibling found for CPU 0.
WARNING: No sibling found for CPU 1.

arch/i386/kernel/mpparse.c

@@ -37,6 +37,7 @@
 
 /* Have we found an MP table */
 int smp_found_config;
+unsigned int __initdata maxcpus = NR_CPUS;
 
 /*
  * Various Linux-internal data structures created from the
@@ -168,8 +169,14 @@ void __init MP_processor_info (struct mpc_config_processor *m)
 	}
 
 	if (num_processors >= NR_CPUS) {
-		printk(KERN_WARNING "NR_CPUS limit of %i reached.  Cannot "
-			"boot CPU(apicid 0x%x).\n", NR_CPUS, m->mpc_apicid);
+		printk(KERN_WARNING "WARNING: NR_CPUS limit of %i reached."
+			"  Processor ignored.\n", NR_CPUS); 
+		return;
+	}
+
+	if (num_processors >= maxcpus) {
+		printk(KERN_WARNING "WARNING: maxcpus limit of %i reached."
+			" Processor ignored.\n", maxcpus); 
 		return;
 	}
 	num_processors++;

arch/i386/kernel/setup.c

@@ -555,6 +555,18 @@ static void __init parse_cmdline_early (char ** cmdline_p)
 			}
 		}
 
+#ifdef  CONFIG_SMP
+		/*
+		 * If the BIOS enumerates physical processors before logical,
+		 * maxcpus=N at enumeration-time can be used to disable HT.
+		 */
+		else if (!memcmp(from, "maxcpus=", 8)) {
+			extern unsigned int maxcpus;
+
+			maxcpus = simple_strtoul(from + 8, NULL, 0);
+		}
+#endif
+
 #ifdef CONFIG_ACPI_BOOT
 		/* "acpi=off" disables both ACPI table parsing and interpreter */
 		else if (!memcmp(from, "acpi=off", 8)) {

arch/x86_64/kernel/mpparse.c

@@ -33,6 +33,7 @@
 
 /* Have we found an MP table */
 int smp_found_config;
+unsigned int __initdata maxcpus = NR_CPUS;
 
 int acpi_found_madt;
 
@@ -117,6 +118,17 @@ static void __init MP_processor_info (struct mpc_config_processor *m)
 		Dprintk("    Bootup CPU\n");
 		boot_cpu_id = m->mpc_apicid;
 	}
+	if (num_processors >= NR_CPUS) {
+		printk(KERN_WARNING "WARNING: NR_CPUS limit of %i reached."
+			" Processor ignored.\n", NR_CPUS);
+		return;
+	}
+	if (num_processors >= maxcpus) {
+		printk(KERN_WARNING "WARNING: maxcpus limit of %i reached."
+			" Processor ignored.\n", maxcpus);
+		return;
+	}
+
 	num_processors++;
 
 	if (m->mpc_apicid > MAX_APICS) {

arch/x86_64/kernel/setup.c

@@ -202,6 +202,17 @@ static __init void parse_cmdline_early (char ** cmdline_p)
 		if (c != ' ') 
 			goto next_char; 
 
+#ifdef  CONFIG_SMP
+		/*
+		 * If the BIOS enumerates physical processors before logical,
+		 * maxcpus=N at enumeration-time can be used to disable HT.
+		 */
+		else if (!memcmp(from, "maxcpus=", 8)) {
+			extern unsigned int maxcpus;
+
+			maxcpus = simple_strtoul(from + 8, NULL, 0);
+		}
+#endif
 #ifdef CONFIG_ACPI_BOOT
 		/* "acpi=off" disables both ACPI table parsing and interpreter init */
 		if (!memcmp(from, "acpi=off", 8))