Currently kdump kernel becomes very slow if 'noapic' is specified.
Normal kernel won't.
Kernel parameter 'noapic' is used to disable IO-APIC in system for
testing or special purpose. Here the root cause is that in kdump
kernel LAPIC is disabled since commit 522e664644
("x86/apic: Disable I/O APIC before shutdown of the local APIC").
In this case We need set up through-local-APIC on boot CPU in
setup_local_APIC().
While In normal kernel the legacy irq mode is enabled in BIOS. If
it is virtual wire mode, the local-APIC has been enabled and set as
through-local-APIC.
Though we fix the regression introduced by criminal commit 522e664644,
for safety and clarity, better set up through-local-APIC explicitly,
but not rely on the default boot irq mode.
Do it now.
Signed-off-by: Baoquan He <b...@redhat.com>
---
arch/x86/kernel/apic/apic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 25ddf02598d2..3fc259b4dd2d 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1570,7 +1570,7 @@ void setup_local_APIC(void)
* TODO: set up through-local-APIC from through-I/O-APIC? --macro
*/
value = apic_read(APIC_LVT0) & APIC_LVT_MASKED;
- if (!cpu && (pic_mode || !value)) {
+ if (!cpu && (pic_mode || !value || skip_ioapic_setup)) {
value = APIC_DM_EXTINT;
apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n", cpu);
} else {
--
2.13.6
