From: Thomas Gleixner Date: Mon, 22 Jul 2019 18:47:08 +0000 (+0200) Subject: x86/apic: Soft disable APIC before initializing it X-Git-Tag: v5.2.19~252 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=9107c9b7bcceed4b47e9335bc8441818e8adf919;p=users%2Fdwmw2%2Flinux.git x86/apic: Soft disable APIC before initializing it [ 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 Acked-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20190722105219.068290579@linutronix.de Signed-off-by: Sasha Levin --- diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 67d1259e0f7c0..a18d6dd934e55 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1550,6 +1550,14 @@ 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) {