x86/apic: Nuke empty init_apic_ldr() callbacks

apic::init_apic_ldr() is only invoked when the APIC is initialized. So
there is really no point in having:

  - Default empty callbacks all over the place

  - Two implementations of the actual LDR init function where one is
    just unreadable gunk but does exactly the same as the other.

Make the apic::init_apic_ldr() invocation conditional, remove the empty
callbacks and consolidate the two implementation into one.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Tested-by: Juergen Gross <jgross@suse.com> # Xen PV (dom0 and unpriv. guest)

arch/x86/include/asm/apic.h

@@ -445,8 +445,6 @@ extern void generic_bigsmp_probe(void);
 
 #include <asm/smp.h>
 
-#define APIC_DFR_VALUE	(APIC_DFR_FLAT)
-
 extern struct apic apic_noop;
 
 static inline unsigned int read_apic_id(void)

arch/x86/kernel/apic/apic.c

@@ -1578,8 +1578,11 @@ static void setup_local_APIC(void)
 	/*
 	 * Intel recommends to set DFR, LDR and TPR before enabling
 	 * an APIC.  See e.g. "AP-388 82489DX User's Manual" (Intel
-	 * document number 292116).  So here it goes...
+	 * document number 292116).
+	 *
+	 * Except for APICs which operate in physical destination mode.
 	 */
+	if (apic->init_apic_ldr)
 		apic->init_apic_ldr();
 
 	/*

arch/x86/kernel/apic/apic_common.c

@@ -6,6 +6,8 @@
 #include <linux/irq.h>
 #include <asm/apic.h>
 
+#include "local.h"
+
 u32 apic_default_calc_apicid(unsigned int cpu)
 {
 	return per_cpu(x86_cpu_to_apicid, cpu);
@@ -39,3 +41,17 @@ int default_apic_id_valid(u32 apicid)
 {
 	return (apicid < 255);
 }
+
+/*
+ * Set up the logical destination ID when the APIC operates in logical
+ * destination mode.
+ */
+void default_init_apic_ldr(void)
+{
+	unsigned long val;
+
+	apic_write(APIC_DFR, APIC_DFR_FLAT);
+	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
+	val |= SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
+	apic_write(APIC_LDR, val);
+}

arch/x86/kernel/apic/apic_flat_64.c

@@ -28,26 +28,6 @@ static int flat_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 	return 1;
 }
 
-/*
- * Set up the logical destination ID.
- *
- * Intel recommends to set DFR, LDR and TPR before enabling
- * an APIC.  See e.g. "AP-388 82489DX User's Manual" (Intel
- * document number 292116).  So here it goes...
- */
-void flat_init_apic_ldr(void)
-{
-	unsigned long val;
-	unsigned long num, id;
-
-	num = smp_processor_id();
-	id = 1UL << num;
-	apic_write(APIC_DFR, APIC_DFR_FLAT);
-	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
-	val |= SET_APIC_LOGICAL_ID(id);
-	apic_write(APIC_LDR, val);
-}
-
 static void _flat_send_IPI_mask(unsigned long mask, int vector)
 {
 	unsigned long flags;
@@ -119,7 +99,7 @@ static struct apic apic_flat __ro_after_init = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= flat_init_apic_ldr,
+	.init_apic_ldr			= default_init_apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,
@@ -175,15 +155,6 @@ static int physflat_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 	return 0;
 }
 
-static void physflat_init_apic_ldr(void)
-{
-	/*
-	 * LDR and DFR are not involved in physflat mode, rather:
-	 * "In physical destination mode, the destination processor is
-	 * specified by its local APIC ID [...]." (Intel SDM, 10.6.2.1)
-	 */
-}
-
 static int physflat_probe(void)
 {
 	if (apic == &apic_physflat || num_possible_cpus() > 8 ||
@@ -207,7 +178,6 @@ static struct apic apic_physflat __ro_after_init = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= physflat_init_apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/kernel/apic/apic_noop.c

@@ -14,7 +14,6 @@
 
 #include <asm/apic.h>
 
-static void noop_init_apic_ldr(void) { }
 static void noop_send_IPI(int cpu, int vector) { }
 static void noop_send_IPI_mask(const struct cpumask *cpumask, int vector) { }
 static void noop_send_IPI_mask_allbutself(const struct cpumask *cpumask, int vector) { }
@@ -94,7 +93,6 @@ struct apic apic_noop __ro_after_init = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= default_check_apicid_used,
-	.init_apic_ldr			= noop_init_apic_ldr,
 	.ioapic_phys_id_map		= default_ioapic_phys_id_map,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/kernel/apic/apic_numachip.c

@@ -252,7 +252,6 @@ static const struct apic apic_numachip1 __refconst = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= flat_init_apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,
@@ -297,7 +296,6 @@ static const struct apic apic_numachip2 __refconst = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= flat_init_apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/kernel/apic/bigsmp_32.c

@@ -28,14 +28,6 @@ static bool bigsmp_check_apicid_used(physid_mask_t *map, int apicid)
 	return false;
 }
 
-/*
- * bigsmp enables physical destination mode
- * and doesn't use LDR and DFR
- */
-static void bigsmp_init_apic_ldr(void)
-{
-}
-
 static void bigsmp_setup_apic_routing(void)
 {
 	printk(KERN_INFO
@@ -108,7 +100,6 @@ static struct apic apic_bigsmp __ro_after_init = {
 	.disable_esr			= 1,
 
 	.check_apicid_used		= bigsmp_check_apicid_used,
-	.init_apic_ldr			= bigsmp_init_apic_ldr,
 	.ioapic_phys_id_map		= bigsmp_ioapic_phys_id_map,
 	.setup_apic_routing		= bigsmp_setup_apic_routing,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/kernel/apic/local.h

@@ -13,9 +13,6 @@
 #include <asm/irq_vectors.h>
 #include <asm/apic.h>
 
-/* APIC flat 64 */
-void flat_init_apic_ldr(void);
-
 /* X2APIC */
 int x2apic_apic_id_valid(u32 apicid);
 int x2apic_apic_id_registered(void);
@@ -46,6 +43,8 @@ static inline unsigned int __prepare_ICR(unsigned int shortcut, int vector,
 	return icr;
 }
 
+void default_init_apic_ldr(void);
+
 void __default_send_IPI_shortcut(unsigned int shortcut, int vector);
 
 /*

arch/x86/kernel/apic/probe_32.c

@@ -32,21 +32,6 @@ static int default_apic_id_registered(void)
 	return physid_isset(read_apic_id(), phys_cpu_present_map);
 }
 
-/*
- * Set up the logical destination ID.  Intel recommends to set DFR, LDR and
- * TPR before enabling an APIC.  See e.g. "AP-388 82489DX User's Manual"
- * (Intel document number 292116).
- */
-static void default_init_apic_ldr(void)
-{
-	unsigned long val;
-
-	apic_write(APIC_DFR, APIC_DFR_VALUE);
-	val = apic_read(APIC_LDR) & ~APIC_LDR_MASK;
-	val |= SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
-	apic_write(APIC_LDR, val);
-}
-
 static int default_phys_pkg_id(int cpuid_apic, int index_msb)
 {
 	return cpuid_apic >> index_msb;

arch/x86/kernel/apic/x2apic_phys.c

@@ -91,10 +91,6 @@ static void x2apic_send_IPI_all(int vector)
 	__x2apic_send_IPI_shorthand(vector, APIC_DEST_ALLINC);
 }
 
-static void init_x2apic_ldr(void)
-{
-}
-
 static int x2apic_phys_probe(void)
 {
 	if (!x2apic_mode)
@@ -169,7 +165,6 @@ static struct apic apic_x2apic_phys __ro_after_init = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= init_x2apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -788,10 +788,6 @@ static int uv_apic_id_registered(void)
 	return 1;
 }
 
-static void uv_init_apic_ldr(void)
-{
-}
-
 static u32 apic_uv_calc_apicid(unsigned int cpu)
 {
 	return apic_default_calc_apicid(cpu);
@@ -841,7 +837,6 @@ static struct apic apic_x2apic_uv_x __ro_after_init = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= NULL,
-	.init_apic_ldr			= uv_init_apic_ldr,
 	.ioapic_phys_id_map		= NULL,
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= default_cpu_present_to_apicid,

arch/x86/xen/apic.c

@@ -149,7 +149,6 @@ static struct apic xen_pv_apic = {
 	.disable_esr			= 0,
 
 	.check_apicid_used		= default_check_apicid_used, /* Used on 32-bit */
-	.init_apic_ldr			= xen_noop, /* setup_local_APIC calls it */
 	.ioapic_phys_id_map		= default_ioapic_phys_id_map, /* Used on 32-bit */
 	.setup_apic_routing		= NULL,
 	.cpu_present_to_apicid		= xen_cpu_present_to_apicid,