| From | Sasha Levin <> | Subject | [PATCH AUTOSEL 4.19 020/128] x86/apic: Soft disable APIC before initializing it | Date | Sun, 22 Sep 2019 14:52:30 -0400 |
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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 9bfbe1fa0339c..dfdd1caf0d55d 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1538,6 +1538,14 @@ static 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) { -- 2.20.1
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