x86/apic: Remove yet another dubious callback

Paranoia is not wrong, but having an APIC callback which is in most
implementations a complete NOOP and in one actually looking whether the
APICID of an upcoming CPU has been registered. The same APICID which was
used to bring the CPU out of wait for startup.

That's paranoia for the paranoia sake. Remove the voodoo.

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/20240212154640.116510935@linutronix.de

6 files changed, 0 insertions, 14 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 89eae0c1e552..ba219d6c851e 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -288,7 +288,6 @@ struct apic {
 	/* Probe, setup and smpboot functions */
 	int	(*probe)(void);
 	int	(*acpi_madt_oem_check)(char *oem_id, char *oem_table_id);
-	bool	(*apic_id_registered)(void);
 
 	void	(*init_apic_ldr)(void);
 	u32	(*cpu_present_to_apicid)(int mps_cpu);
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index e3cebd45526b..68767a9dd3d1 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1538,9 +1538,6 @@ static void setup_local_APIC(void)
 		apic_write(APIC_ESR, 0);
 	}
 #endif
-	/* Validate that the APIC is registered if required */
-	BUG_ON(apic->apic_id_registered && !apic->apic_id_registered());
-
 	/*
 	 * Intel recommends to set DFR, LDR and TPR before enabling
 	 * an APIC.  See e.g. "AP-388 82489DX User's Manual" (Intel
diff --git a/arch/x86/kernel/apic/apic_common.c b/arch/x86/kernel/apic/apic_common.c
index d4dfa437081a..9ef3be866832 100644
--- a/arch/x86/kernel/apic/apic_common.c
+++ b/arch/x86/kernel/apic/apic_common.c
@@ -27,11 +27,6 @@ u32 default_cpu_present_to_apicid(int mps_cpu)
 }
 EXPORT_SYMBOL_GPL(default_cpu_present_to_apicid);
 
-bool default_apic_id_registered(void)
-{
-	return test_bit(read_apic_id(), phys_cpu_present_map);
-}
-
 /*
  * Set up the logical destination ID when the APIC operates in logical
  * destination mode.
diff --git a/arch/x86/kernel/apic/apic_flat_64.c b/arch/x86/kernel/apic/apic_flat_64.c
index f6ef12126ba1..f37ad3392fec 100644
--- a/arch/x86/kernel/apic/apic_flat_64.c
+++ b/arch/x86/kernel/apic/apic_flat_64.c
@@ -70,7 +70,6 @@ static struct apic apic_flat __ro_after_init = {
 	.name				= "flat",
 	.probe				= flat_probe,
 	.acpi_madt_oem_check		= flat_acpi_madt_oem_check,
-	.apic_id_registered		= default_apic_id_registered,
 
 	.dest_mode_logical		= true,
 
@@ -139,7 +138,6 @@ static struct apic apic_physflat __ro_after_init = {
 	.name				= "physical flat",
 	.probe				= physflat_probe,
 	.acpi_madt_oem_check		= physflat_acpi_madt_oem_check,
-	.apic_id_registered		= default_apic_id_registered,
 
 	.dest_mode_logical		= false,
 
diff --git a/arch/x86/kernel/apic/local.h b/arch/x86/kernel/apic/local.h
index f8a87f9e72e6..842fe28496be 100644
--- a/arch/x86/kernel/apic/local.h
+++ b/arch/x86/kernel/apic/local.h
@@ -61,8 +61,6 @@ void default_send_IPI_allbutself(int vector);
 void default_send_IPI_all(int vector);
 void default_send_IPI_self(int vector);
 
-bool default_apic_id_registered(void);
-
 #ifdef CONFIG_X86_32
 void default_send_IPI_mask_sequence_logical(const struct cpumask *mask, int vector);
 void default_send_IPI_mask_allbutself_logical(const struct cpumask *mask, int vector);
diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
index cdf4047d88e1..f75ee345c02d 100644
--- a/arch/x86/kernel/apic/probe_32.c
+++ b/arch/x86/kernel/apic/probe_32.c
@@ -38,7 +38,6 @@ static struct apic apic_default __ro_after_init = {
 
 	.name				= "default",
 	.probe				= probe_default,
-	.apic_id_registered		= default_apic_id_registered,
 
 	.dest_mode_logical		= true,