[PATCH v2 2/4] x86/apic: Consolidate early APIC initialization into apic_early_init()

[Grzegorz Jaszczyk]

Early APIC initialization is currently scattered across setup_arch():
apic_setup_apic_calls() and acpi_mps_check() run early, check_x2apic()
is invoked much later during memory range setup, and
apic_finalize_early_init() runs near the end of setup_arch().

Consolidate the initial setup into apic_early_init() in
arch/x86/kernel/apic/apic.c so that acpi_mps_check(), check_x2apic(),
and static call initialization happen together in one place. Make
check_x2apic() static as it no longer has external callers.

Place apic_setup_apic_calls() at the end of apic_early_init() in
preparation for replacing it with apic_install_default_driver() in the
subsequent patch. This ordering change is safe because neither
acpi_mps_check() nor check_x2apic() uses APIC static calls
(check_x2apic() accesses x2APIC MSRs directly via native_apic_msr_read()).

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Grzegorz Jaszczyk <jaszczyk@xxxxxxxxxxxx>
---
 arch/x86/include/asm/apic.h |  3 ++-
 arch/x86/kernel/apic/apic.c | 16 ++++++++++++++--
 arch/x86/kernel/setup.c     | 10 +---------
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index b4c112b6d3ab3..b1610b8bc6544 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -133,6 +133,7 @@ extern void sync_Arb_IDs(void);
 extern void init_bsp_APIC(void);
 extern void apic_intr_mode_select(void);
 extern void apic_intr_mode_init(void);
+void apic_early_init(void);
 void apic_finalize_early_init(void);
 void register_lapic_address(unsigned long address);
 extern void setup_boot_APIC_clock(void);
@@ -183,6 +184,7 @@ extern void topology_reset_possible_cpus_up(void);
 #else /* !CONFIG_X86_LOCAL_APIC */
 static inline void lapic_shutdown(void) { }
 #define local_apic_timer_c2_ok		1
+static inline void apic_early_init(void) { }
 static inline void apic_finalize_early_init(void) { }
 static inline void disable_local_APIC(void) { }
 # define setup_boot_APIC_clock x86_init_noop
@@ -254,7 +256,6 @@ static inline u32 native_apic_msr_read(u32 reg) { BUG(); }
 #define x2apic_mode		(0)
 #define	x2apic_supported()	(0)
 #endif /* !CONFIG_X86_X2APIC */
-extern void __init check_x2apic(void);
 
 struct irq_data;
 
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index cb78e0d6c9317..721e194ceac2d 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1869,7 +1869,7 @@ static __init void try_to_enable_x2apic(int remap_mode)
 	x2apic_enable();
 }
 
-void __init check_x2apic(void)
+static void __init check_x2apic(void)
 {
 	if (x2apic_enabled()) {
 		pr_info("x2apic: enabled by BIOS, switching to x2apic ops\n");
@@ -1884,7 +1884,7 @@ void __init check_x2apic(void)
 	}
 }
 #else /* CONFIG_X86_X2APIC */
-void __init check_x2apic(void)
+static void __init check_x2apic(void)
 {
 	if (!apic_is_x2apic_enabled())
 		return;
@@ -2064,6 +2064,18 @@ static bool __init detect_init_APIC(void)
 }
 #endif
 
+void __init apic_early_init(void)
+{
+	if (acpi_mps_check()) {
+		apic_is_disabled = true;
+		setup_clear_cpu_cap(X86_FEATURE_APIC);
+	} else {
+		check_x2apic();
+	}
+
+	apic_setup_apic_calls();
+}
+
 void __init apic_finalize_early_init(void)
 {
 	if (apic_validate_deadline_timer())
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 06522a205dd93..2bab41e073d52 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -993,14 +993,7 @@ void __init setup_arch(char **cmdline_p)
 
 	x86_report_nx();
 
-	apic_setup_apic_calls();
-
-	if (acpi_mps_check()) {
-#ifdef CONFIG_X86_LOCAL_APIC
-		apic_is_disabled = true;
-#endif
-		setup_clear_cpu_cap(X86_FEATURE_APIC);
-	}
+	apic_early_init();
 
 	e820__finish_early_params();
 
@@ -1062,7 +1055,6 @@ void __init setup_arch(char **cmdline_p)
 	/* max_low_pfn get updated here */
 	find_low_pfn_range();
 #else
-	check_x2apic();
 
 	/* How many end-of-memory variables you have, grandma! */
 	/* need this before calling reserve_initrd */
-- 
2.56.0.rc1.315.gc6ed9934b7-goog