From: Baoquan He <bhe@redhat.com>
Date: Wed, 14 Feb 2018 13:46:56 +0800
Subject: x86/apic: Set up through-local-APIC mode on the boot CPU if 'noapic'
specified
Git-commit: bee3204ec3c49f6f53add9c3962c9012a5c036fa
Patch-mainline: v4.17-rc1
References: bsc#1110006
Currently the kdump kernel becomes very slow if 'noapic' is specified.
Normal kernel doesn't have this bug.
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().
In normal kernel the legacy irq mode is enabled by the BIOS. If
it is virtual wire mode, the local-APIC has been enabled and set as
through-local-APIC.
Though we fixed the regression introduced by commit 522e664644,
to further improve robustness set up the through-local-APIC mode
explicitly, do not rely on the default boot IRQ mode.
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: douly.fnst@cn.fujitsu.com
Cc: joro@8bytes.org
Cc: prarit@redhat.com
Cc: uobergfe@redhat.com
Link: http://lkml.kernel.org/r/20180214054656.3780-7-bhe@redhat.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
---
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 871018dd49a3..2ceac9f6c5d7 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1570,7 +1570,7 @@ static 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 {