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Date:   Thu, 04 Jul 2019 17:51:48 +0200
From:   Thomas Gleixner <>
To:     LKML <>
Cc:, Nadav Amit <>,
        Ricardo Neri <>,
        Stephane Eranian <>,
        Feng Tang <>
Subject: [patch V2 03/25] x86/apic: Soft disable APIC before initializing it

If the APIC was already enabled on entry of setup_local_APIC() then
disabling it soft via the SPIV register makes a lot of sense.

That masks all LVT entries and brings it into a well defined state.

Otherwise previously enabled LVTs which are not touched in the setup
function stay unmasked and might surprise the just booting kernel.

Signed-off-by: Thomas Gleixner <>
 arch/x86/kernel/apic/apic.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1493,6 +1493,14 @@ static void setup_local_APIC(void)
+	/*
+	 * If this comes from kexec/kcrash the APIC might be enabled in
+	 * SPIV. Soft disable it before doing further initialization.
+	 */
+	value = apic_read(APIC_SPIV);
+	apic_write(APIC_SPIV, value);
 #ifdef CONFIG_X86_32
 	/* Pound the ESR really hard over the head with a big hammer - mbligh */
 	if (lapic_is_integrated() && apic->disable_esr) {

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