4.16-stable review patch. If anyone has any objections, please let me know.
------------------ From: Baoquan He <[email protected]> [ Upstream commit bee3204ec3c49f6f53add9c3962c9012a5c036fa ] 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 <[email protected]> Reviewed-by: Eric W. Biederman <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] [ Rewrote the changelog. ] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/kernel/apic/apic.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- 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 {
