[PATCH v2 1/2] x86/smpboot: Check APIC ID before setting up default routing

* [PATCH v2 1/2] x86/smpboot: Check APIC ID before setting up default routing
@ 2016-08-19  3:22 Wei Jiangang
  2016-08-19  3:22 ` [PATCH v2 2/2] x86/apic: Update comment about disabling processor focus Wei Jiangang
  2016-08-24 13:01 ` [tip:x86/apic] x86/smpboot: Check APIC ID before setting up default routing tip-bot for Wei Jiangang
  0 siblings, 2 replies; 4+ messages in thread
From: Wei Jiangang @ 2016-08-19  3:22 UTC (permalink / raw)
  To: linux-kernel; +Cc: x86, tglx, mingo, hpa, bp, Wei Jiangang

This is not a bugfix, but code optimization.

If the BSP's APIC ID in local APIC is unexpected,
a kernel panic will occur and the system will halt.
That means no need to enable APIC mode, and no reason
to set up the default routing for APIC.

The combination of default_setup_apic_routing() and
apic_bsp_setup() are used to enable APIC mode.
They two should be kept together, rather than being
separated by the codes of checking APIC ID.
Just like their usage in APIC_init_uniprocessor().

Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
---
 arch/x86/kernel/smpboot.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2a6e84a30a54..8216b997c1c9 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1316,14 +1316,13 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 		break;
 	}
 
-	default_setup_apic_routing();
-
 	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);
 
 	pr_info("CPU%d: ", 0);
-- 
1.9.3

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