[PATCH] Summit sub-arch: Make logical IDs independent of BIOS numbering scheme

From: James Cleverdon <jamesclv@us.ibm.com>

In forthcoming IBM x445 systems, the physical APIC ID will not follow the
simple rule laid out by Intel and encoded into xapic_phys_to_log_apicid.
(The BIOS code that sets IDs doesn't work right above 16 CPUs if HT is turned 
on, so for > 16-way the BIOS will disable HT and repack the physical CPUs
into APIC clusters.)

Anyway, it's a good idea to make the APIC code more independent of any
particular BIOS numbering scheme.  This patch allocates logical IDs based on
how many CPUs have already been onlined in a particular APIC cluster.

include/asm-i386/mach-summit/mach_apic.h

@@ -7,14 +7,11 @@
 #define esr_disable (1)
 #define NO_BALANCE_IRQ (0)
 
-#define XAPIC_DEST_CPUS_MASK    0x0Fu
-#define XAPIC_DEST_CLUSTER_MASK 0xF0u
-
-static inline unsigned long xapic_phys_to_log_apicid(int phys_apic) 
-{
-	return ( (1ul << ((phys_apic) & 0x3)) |
-		 ((phys_apic) & XAPIC_DEST_CLUSTER_MASK) );
-}
+/* In clustered mode, the high nibble of APIC ID is a cluster number.
+ * The low nibble is a 4-bit bitmap. */
+#define XAPIC_DEST_CPUS_SHIFT	4
+#define XAPIC_DEST_CPUS_MASK	((1u << XAPIC_DEST_CPUS_SHIFT) - 1)
+#define XAPIC_DEST_CLUSTER_MASK	(XAPIC_DEST_CPUS_MASK << XAPIC_DEST_CPUS_SHIFT)
 
 #define APIC_DFR_VALUE	(APIC_DFR_CLUSTER)
 
@@ -40,15 +37,29 @@ static inline unsigned long check_apicid_present(int bit)
 	return 1;
 }
 
-#define apicid_cluster(apicid) (apicid & 0xF0)
+#define apicid_cluster(apicid) ((apicid) & XAPIC_DEST_CLUSTER_MASK)
 
 extern u8 bios_cpu_apicid[];
+extern u8 cpu_2_logical_apicid[];
 
 static inline void init_apic_ldr(void)
 {
 	unsigned long val, id;
-
-	id = xapic_phys_to_log_apicid(hard_smp_processor_id());
+	int i, count;
+	u8 lid;
+	u8 my_id = (u8)hard_smp_processor_id();
+	u8 my_cluster = (u8)apicid_cluster(my_id);
+
+	/* Create logical APIC IDs by counting CPUs already in cluster. */
+	for (count = 0, i = NR_CPUS; --i >= 0; ) {
+		lid = cpu_2_logical_apicid[i];
+		if (lid != BAD_APICID && apicid_cluster(lid) == my_cluster)
+			++count;
+	}
+	/* We only have a 4 wide bitmap in cluster mode.  If a deranged
+	 * BIOS puts 5 CPUs in one APIC cluster, we're hosed. */
+	BUG_ON(count >= XAPIC_DEST_CPUS_SHIFT);
+	id = my_cluster | (1UL << count);
 	apic_write_around(APIC_DFR, APIC_DFR_VALUE);
 	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
 	val |= SET_APIC_LOGICAL_ID(id);
@@ -77,7 +88,6 @@ static inline int apicid_to_node(int logical_apicid)
 }
 
 /* Mapping from cpu number to logical apicid */
-extern u8 cpu_2_logical_apicid[];
 static inline int cpu_to_logical_apicid(int cpu)
 {
        if (cpu >= NR_CPUS)