[PATCH] Do not enforce unique IO_APIC_ID check for xAPIC systems (i386)

This patch is per Andi's request to remove NO_IOAPIC_CHECK from genapic and
use heuristics to prevent unique I/O APIC ID check for systems that don't
need it.  The patch disables unique I/O APIC ID check for Xeon-based and
other platforms that don't use serial APIC bus for interrupt delivery.
Andi stated that AMD systems don't need unique IO_APIC_IDs either.

Signed-off-by: Natalie Protasevich <Natalie.Protasevich@unisys.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/io_apic.c

@@ -1658,6 +1658,12 @@ static void __init setup_ioapic_ids_from_mpc(void)
 	unsigned char old_id;
 	unsigned long flags;
 
+	/*
+	 * Don't check I/O APIC IDs for xAPIC systems.  They have
+	 * no meaning without the serial APIC bus.
+	 */
+	if (!(boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && boot_cpu_data.x86 < 15))
+		return;
 	/*
 	 * This is broken; anything with a real cpu count has to
 	 * circumvent this idiocy regardless.
@@ -1684,10 +1690,6 @@ static void __init setup_ioapic_ids_from_mpc(void)
 			mp_ioapics[apic].mpc_apicid = reg_00.bits.ID;
 		}
 
-		/* Don't check I/O APIC IDs for some xAPIC systems.  They have
-		 * no meaning without the serial APIC bus. */
-		if (NO_IOAPIC_CHECK)
-			continue;
 		/*
 		 * Sanity check, is the ID really free? Every APIC in a
 		 * system must have a unique ID or we get lots of nice

arch/i386/kernel/mpparse.c

@@ -914,7 +914,10 @@ void __init mp_register_ioapic (
 	mp_ioapics[idx].mpc_apicaddr = address;
 
 	set_fixmap_nocache(FIX_IO_APIC_BASE_0 + idx, address);
-	mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id);
+	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 < 15))
+		mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id);
+	else
+		mp_ioapics[idx].mpc_apicid = id;
 	mp_ioapics[idx].mpc_apicver = io_apic_get_version(idx);
 	
 	/* 

include/asm-i386/genapic.h

@@ -78,7 +78,6 @@ struct genapic {
 	.int_delivery_mode = INT_DELIVERY_MODE, \
 	.int_dest_mode = INT_DEST_MODE, \
 	.no_balance_irq = NO_BALANCE_IRQ, \
-	.no_ioapic_check = NO_IOAPIC_CHECK, \
 	.ESR_DISABLE = esr_disable, \
 	.apic_destination_logical = APIC_DEST_LOGICAL, \
 	APICFUNC(apic_id_registered), \

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

@@ -14,8 +14,6 @@
 #define NO_BALANCE_IRQ (1)
 #define esr_disable (1)
 
-#define NO_IOAPIC_CHECK (0)
-
 static inline int apic_id_registered(void)
 {
 	return (1);

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

@@ -19,8 +19,6 @@ static inline cpumask_t target_cpus(void)
 #define NO_BALANCE_IRQ (0)
 #define esr_disable (0)
 
-#define NO_IOAPIC_CHECK (0)
-
 #define INT_DELIVERY_MODE dest_LowestPrio
 #define INT_DEST_MODE 1     /* logical delivery broadcast to all procs */
 

include/asm-i386/mach-es7000/mach_apic.h

@@ -38,8 +38,6 @@ static inline cpumask_t target_cpus(void)
 #define WAKE_SECONDARY_VIA_INIT
 #endif
 
-#define NO_IOAPIC_CHECK (1)
-
 static inline unsigned long check_apicid_used(physid_mask_t bitmap, int apicid)
 { 
 	return 0;

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

@@ -5,7 +5,6 @@
 
 #define esr_disable (genapic->ESR_DISABLE)
 #define NO_BALANCE_IRQ (genapic->no_balance_irq)
-#define NO_IOAPIC_CHECK	(genapic->no_ioapic_check)
 #define INT_DELIVERY_MODE (genapic->int_delivery_mode)
 #define INT_DEST_MODE (genapic->int_dest_mode)
 #undef APIC_DEST_LOGICAL

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

@@ -17,8 +17,6 @@ static inline cpumask_t target_cpus(void)
 #define NO_BALANCE_IRQ (1)
 #define esr_disable (1)
 
-#define NO_IOAPIC_CHECK (0)
-
 #define INT_DELIVERY_MODE dest_LowestPrio
 #define INT_DEST_MODE 0     /* physical delivery on LOCAL quad */
  

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

@@ -7,8 +7,6 @@
 #define esr_disable (1)
 #define NO_BALANCE_IRQ (0)
 
-#define NO_IOAPIC_CHECK (1)	/* Don't check I/O APIC ID for xAPIC */
-
 /* 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

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

@@ -9,8 +9,6 @@
 #define no_balance_irq (0)
 #define esr_disable (0)
 
-#define NO_IOAPIC_CHECK (0)
-
 #define INT_DELIVERY_MODE dest_LowestPrio
 #define INT_DEST_MODE 1     /* logical delivery broadcast to all procs */