From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 2640da4cccf5cc613bf26f0998b9e340f4b5f69c ]
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 tglx@linutronix.de Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20190722105219.068290579@linutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/kernel/apic/apic.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index f8f9cfded97d3..ea2de324ab021 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1384,6 +1384,14 @@ void setup_local_APIC(void) return; }
+ /* + * 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); + value &= ~APIC_SPIV_APIC_ENABLED; + 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) {