[RFC PATCH v2 03/12] x86/apic: Prepare for unifying the interrupt delivery modes setup

[Dou Liyang]

There are three positions for initializing the interrupt delivery
modes:

1) In IRQ initial function, may setup the through-local-APIC
   virtual wire mode.

2) In an SMP-capable system, will try to switch to symmetric I/O
   model when preparing the cpus in native_smp_prepare_cpus().

3) In UP system with UP_LATE_INIT=y, will set up local APIC and
   I/O APIC in smp_init().

Switching to symmetric I/O model is so late, which causes the
dump-capture kernel hangs with 'notsc' option inherited from 1st kernel
option.

Preparatory patch to initialize an interrupt mode directly and provide
a new function init_interrupt_mode() to unify that three positions and
do that setup as soon as possible.

Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/include/asm/apic.h |  2 ++
 arch/x86/kernel/apic/apic.c | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 86597f3..64f30ee3 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -128,6 +128,7 @@ extern void disable_local_APIC(void);
 extern void lapic_shutdown(void);
 extern void sync_Arb_IDs(void);
 extern void apic_virtual_wire_mode_setup(void);
+extern void init_interrupt_mode(void);
 extern void setup_local_APIC(void);
 extern void init_apic_mappings(void);
 void register_lapic_address(unsigned long address);
@@ -171,6 +172,7 @@ static inline void disable_local_APIC(void) { }
 # define setup_secondary_APIC_clock x86_init_noop
 static inline void lapic_update_tsc_freq(void) { }
 static inline void apic_virtual_wire_mode_setup(void) {}
+static inline void init_interrupt_mode(void) {}
 #endif /* !CONFIG_X86_LOCAL_APIC */
 
 #ifdef CONFIG_X86_X2APIC
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index c754e48..8ac4f58 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1259,6 +1259,22 @@ void __init apic_virtual_wire_mode_setup(void)
 	apic_write(APIC_LVT1, value);
 }
 
+/* Init the interrupt delivery mode for the BSP */
+void __init init_interrupt_mode(void)
+{
+	switch (apic_bsp_mode_check()) {
+	case APIC_PIC:
+		pr_info("Keep in PIC mode(8259)\n");
+		return;
+	case APIC_VIRTUAL_WIRE:
+		pr_info("Switch to virtual wire mode\n");
+		return;
+	case APIC_SYMMETRIC_IO:
+		pr_info("Switch to symmectic I/O mode\n");
+		return;
+	}
+}
+
 static void lapic_setup_esr(void)
 {
 	unsigned int oldvalue, value, maxlvt;
-- 
2.5.5