[RFC PATCH v4 09/12] x86/apic: Setup interrupt mode earlier in case of no SMP motherboard

[Dou Liyang <douly.fnst@cn.fujitsu.com>]

Kernel falls back to non SMP mode and sets up interrupt delivery mode
in APIC_init_uniprocessor() in case of no SMP motherboard.

Setting up interrupt delivery mode as soon as possible should wraps
this case for SMP-capable system too.

Wrap this case, make it consistent with SMP-capable systems.
Incidentally,
 -Extract apic_bsp_setup() and Refine apic_interrupt_mode_init().

Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
---
Sorry to trouble again, I tested a bug, update the patch to fix it.

V3 --> V4:
  - Replace "return" with "break" in case of APIC_SYMMETRIC_IO_NO_ROUTING

V2 --> V3:
  - Replace APIC_SYMMETRIC_IO_NO_CONFIG with APIC_VIRTUAL_WIRE_NO_CONFIG
  - Do some cleanup.

 arch/x86/kernel/apic/apic.c | 25 +++++++++++++++++--------
 arch/x86/kernel/smpboot.c   |  2 --
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 941ae1e..1c93c65 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1160,12 +1160,13 @@ void __init sync_Arb_IDs(void)
 enum apic_interrupt_mode {
 	APIC_PIC = 0,
 	APIC_VIRTUAL_WIRE,
+	APIC_VIRTUAL_WIRE_NO_CONFIG,
 	APIC_SYMMETRIC_IO,
 	APIC_SYMMETRIC_IO_NO_ROUTING,
 	APIC_MODE_COUNT
 };
 
-static int __init apic_interrupt_mode_select(void)
+static int __init apic_interrupt_mode_select(int *upmode)
 {
 	/* Check kernel option */
 	if (disable_apic) {
@@ -1208,8 +1209,12 @@ static int __init apic_interrupt_mode_select(void)
 	if (!smp_found_config) {
 		disable_ioapic_support();
 
-		if (!acpi_lapic)
+		if (!acpi_lapic) {
 			pr_info("ACPI MADT or MP table not detected\n");
+			*upmode = true;
+
+			return APIC_VIRTUAL_WIRE_NO_CONFIG;
+		}
 
 		return APIC_VIRTUAL_WIRE;
 	}
@@ -1285,23 +1290,27 @@ void __init apic_virtual_wire_mode_setup(void)
 /* Init the interrupt delivery mode for the BSP */
 void __init apic_interrupt_mode_init(void)
 {
-	switch (apic_interrupt_mode_select()) {
+	int upmode = false;
+
+	switch (apic_interrupt_mode_select(&upmode)) {
 	case APIC_PIC:
 		pr_info("Keep in PIC mode(8259)\n");
 		return;
 	case APIC_VIRTUAL_WIRE:
+	case APIC_VIRTUAL_WIRE_NO_CONFIG:
 		pr_info("Switch to virtual wire mode\n");
-		return;
+		default_setup_apic_routing();
+		break;
 	case APIC_SYMMETRIC_IO:
 		pr_info("Switch to symmectic I/O mode\n");
 		default_setup_apic_routing();
-		apic_bsp_setup(false);
-		return;
+		break;
 	case APIC_SYMMETRIC_IO_NO_ROUTING:
 		pr_info("Switch to symmectic I/O mode with no APIC routing\n");
-		apic_bsp_setup(false);
-		return;
+		break;
 	}
+
+	apic_bsp_setup(upmode);
 }
 
 static void lapic_setup_esr(void)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2101d5c..6e8c39b 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1324,8 +1324,6 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 	switch (smp_sanity_check(max_cpus)) {
 	case SMP_NO_CONFIG:
 		disable_smp();
-		if (APIC_init_uniprocessor())
-			pr_notice("Local APIC not detected. Using dummy APIC emulation.\n");
 		return;
 	case SMP_NO_APIC:
 		disable_smp();
-- 
2.5.5