x86/apic: Remove the pointless writeback of boot_cpu_physical_apicid

There is absolutely no point to write the APIC ID which was read from the
local APIC earlier, back into the local APIC for the 64-bit UP case.

Remove that along with the apic callback which is solely there for this
pointless exercise.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Sohil Mehta <sohil.mehta@intel.com>
Link: https://lore.kernel.org/r/20240212154640.055288922@linutronix.de

arch/x86/include/asm/apic.h

@@ -294,7 +294,6 @@ struct apic {
 	u32	(*cpu_present_to_apicid)(int mps_cpu);
 
 	u32	(*get_apic_id)(u32 id);
-	u32	(*set_apic_id)(u32 apicid);
 
 	/* wakeup_secondary_cpu */
 	int	(*wakeup_secondary_cpu)(u32 apicid, unsigned long start_eip);

arch/x86/kernel/apic/apic.c

@@ -2485,9 +2485,6 @@ EXPORT_SYMBOL_GPL(x86_msi_msg_get_destid);
 
 static void __init apic_bsp_up_setup(void)
 {
-#ifdef CONFIG_X86_64
-	apic_write(APIC_ID, apic->set_apic_id(boot_cpu_physical_apicid));
-#endif
 	reset_phys_cpu_present_map(boot_cpu_physical_apicid);
 }
 

arch/x86/kernel/apic/apic_flat_64.c

@@ -61,11 +61,6 @@ static u32 flat_get_apic_id(u32 x)
 	return (x >> 24) & 0xFF;
 }
 
-static u32 set_apic_id(u32 id)
-{
-	return (id & 0xFF) << 24;
-}
-
 static int flat_probe(void)
 {
 	return 1;
@@ -86,7 +81,6 @@ static struct apic apic_flat __ro_after_init = {
 
 	.max_apic_id			= 0xFE,
 	.get_apic_id			= flat_get_apic_id,
-	.set_apic_id			= set_apic_id,
 
 	.calc_dest_apicid		= apic_flat_calc_apicid,
 
@@ -155,7 +149,6 @@ static struct apic apic_physflat __ro_after_init = {
 
 	.max_apic_id			= 0xFE,
 	.get_apic_id			= flat_get_apic_id,
-	.set_apic_id			= set_apic_id,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 

arch/x86/kernel/apic/apic_numachip.c

@@ -38,11 +38,6 @@ static u32 numachip1_get_apic_id(u32 x)
 	return id;
 }
 
-static u32 numachip1_set_apic_id(u32 id)
-{
-	return (id & 0xff) << 24;
-}
-
 static u32 numachip2_get_apic_id(u32 x)
 {
 	u64 mcfg;
@@ -51,11 +46,6 @@ static u32 numachip2_get_apic_id(u32 x)
 	return ((mcfg >> (28 - 8)) & 0xfff00) | (x >> 24);
 }
 
-static u32 numachip2_set_apic_id(u32 id)
-{
-	return id << 24;
-}
-
 static void numachip1_apic_icr_write(int apicid, unsigned int val)
 {
 	write_lcsr(CSR_G3_EXT_IRQ_GEN, (apicid << 16) | val);
@@ -225,7 +215,6 @@ static const struct apic apic_numachip1 __refconst = {
 
 	.max_apic_id			= UINT_MAX,
 	.get_apic_id			= numachip1_get_apic_id,
-	.set_apic_id			= numachip1_set_apic_id,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 
@@ -260,7 +249,6 @@ static const struct apic apic_numachip2 __refconst = {
 
 	.max_apic_id			= UINT_MAX,
 	.get_apic_id			= numachip2_get_apic_id,
-	.set_apic_id			= numachip2_set_apic_id,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 

arch/x86/kernel/apic/bigsmp_32.c

@@ -72,7 +72,6 @@ static struct apic apic_bigsmp __ro_after_init = {
 
 	.max_apic_id			= 0xFE,
 	.get_apic_id			= bigsmp_get_apic_id,
-	.set_apic_id			= NULL,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 

arch/x86/kernel/apic/local.h

@@ -16,7 +16,6 @@
 /* X2APIC */
 void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest);
 u32 x2apic_get_apic_id(u32 id);
-u32 x2apic_set_apic_id(u32 id);
 
 void x2apic_send_IPI_all(int vector);
 void x2apic_send_IPI_allbutself(int vector);

arch/x86/kernel/apic/x2apic_cluster.c

@@ -237,7 +237,6 @@ static struct apic apic_x2apic_cluster __ro_after_init = {
 	.max_apic_id			= UINT_MAX,
 	.x2apic_set_max_apicid		= true,
 	.get_apic_id			= x2apic_get_apic_id,
-	.set_apic_id			= x2apic_set_apic_id,
 
 	.calc_dest_apicid		= x2apic_calc_apicid,
 

arch/x86/kernel/apic/x2apic_phys.c

@@ -129,11 +129,6 @@ u32 x2apic_get_apic_id(u32 id)
 	return id;
 }
 
-u32 x2apic_set_apic_id(u32 id)
-{
-	return id;
-}
-
 static struct apic apic_x2apic_phys __ro_after_init = {
 
 	.name				= "physical x2apic",
@@ -149,7 +144,6 @@ static struct apic apic_x2apic_phys __ro_after_init = {
 	.max_apic_id			= UINT_MAX,
 	.x2apic_set_max_apicid		= true,
 	.get_apic_id			= x2apic_get_apic_id,
-	.set_apic_id			= x2apic_set_apic_id,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -745,11 +745,6 @@ static void uv_send_IPI_all(int vector)
 	uv_send_IPI_mask(cpu_online_mask, vector);
 }
 
-static u32 set_apic_id(u32 id)
-{
-	return id;
-}
-
 static int uv_probe(void)
 {
 	return apic == &apic_x2apic_uv_x;
@@ -769,7 +764,6 @@ static struct apic apic_x2apic_uv_x __ro_after_init = {
 
 	.max_apic_id			= UINT_MAX,
 	.get_apic_id			= x2apic_get_apic_id,
-	.set_apic_id			= set_apic_id,
 
 	.calc_dest_apicid		= apic_default_calc_apicid,
 

arch/x86/xen/apic.c

@@ -33,12 +33,6 @@ static unsigned int xen_io_apic_read(unsigned apic, unsigned reg)
 	return 0xfd;
 }
 
-static u32 xen_set_apic_id(u32 x)
-{
-	WARN_ON(1);
-	return x;
-}
-
 static u32 xen_get_apic_id(u32 x)
 {
 	return ((x)>>24) & 0xFFu;
@@ -131,7 +125,6 @@ static struct apic xen_pv_apic __ro_after_init = {
 
 	.max_apic_id			= UINT_MAX,
 	.get_apic_id			= xen_get_apic_id,
-	.set_apic_id			= xen_set_apic_id,
 
 	.calc_dest_apicid		= apic_flat_calc_apicid,