[RFC PATCH v2 08/12] x86/apic: Make the interrupt mode setup earlier for SMP-capable system

[Dou Liyang]

In the SMP-capable system, enable and setup the interrupt delivery
mode in native_smp_prepare_cpus() which almost be called at the end of
start_kernel().

But, calibrate delay needs the timer interrupt which may be disabled
in dump-capture kernel.

Due to the MP table or ACPI has been read earlier, setup the interrupt
mode as soon as possible to cleanup the disabled situation for
SMP-capable system.

Signed-off-by: Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/kernel/apic/apic.c | 21 +++++++++++++++++++++
 arch/x86/kernel/smpboot.c   | 10 ----------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index f726c4f..170cd1a 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1157,6 +1157,7 @@ enum apic_interrupt_mode {
 	APIC_PIC = 0,
 	APIC_VIRTUAL_WIRE,
 	APIC_SYMMETRIC_IO,
+	APIC_SYMMETRIC_IO_NO_ROUTING,
 	APIC_MODE_COUNT
 };
 
@@ -1207,6 +1208,20 @@ static int __init apic_bsp_mode_check(void)
 
 	/* Other checks of ACPI options will be done in each setup function */
 
+#ifdef CONFIG_SMP
+	if (read_apic_id() != boot_cpu_physical_apicid) {
+		panic("Boot APIC ID in local APIC unexpected (%d vs %d)",
+		     read_apic_id(), boot_cpu_physical_apicid);
+		/* Or can we switch back to PIC here? */
+	}
+
+	/* If SMP should be disabled, then really disable it! */
+	if (!setup_max_cpus) {
+		pr_info("SMP mode deactivated\n");
+		return APIC_SYMMETRIC_IO_NO_ROUTING;
+	}
+#endif
+
 	return APIC_SYMMETRIC_IO;
 }
 
@@ -1271,6 +1286,12 @@ void __init init_interrupt_mode(void)
 		return;
 	case APIC_SYMMETRIC_IO:
 		pr_info("Switch to symmectic I/O mode\n");
+		default_setup_apic_routing();
+		apic_bsp_setup(false);
+		return;
+	case APIC_SYMMETRIC_IO_NO_ROUTING:
+		pr_info("Switch to symmectic I/O mode with no APIC routing\n");
+		apic_bsp_setup(false);
 		return;
 	}
 }
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 830b01b..345ad20 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1332,21 +1332,11 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 		return;
 	case SMP_FORCE_UP:
 		disable_smp();
-		apic_bsp_setup(false);
 		return;
 	case SMP_OK:
 		break;
 	}
 
-	if (read_apic_id() != boot_cpu_physical_apicid) {
-		panic("Boot APIC ID in local APIC unexpected (%d vs %d)",
-		     read_apic_id(), boot_cpu_physical_apicid);
-		/* Or can we switch back to PIC here? */
-	}
-
-	default_setup_apic_routing();
-	cpu0_logical_apicid = apic_bsp_setup(false);
-
 	if (x2apic_mode)
 		cpu0_logical_apicid = apic_read(APIC_LDR);
 	else
-- 
2.5.5