From 77f72b192fd4624ad639dbf60c48be787c8aea59 Mon Sep 17 00:00:00 2001 From: Zwane Mwaikambo Date: Mon, 7 Nov 2005 00:58:33 -0800 Subject: [PATCH] [PATCH] i386: LVT entries remaining unmasked on reboot Excerpt from bugzilla entry http://bugzilla.kernel.org/show_bug.cgi?id=5518 "i386 version of Reboot-through-BIOS is unsafe: it forgets to mask APIC LVT interrupts before jumping to a BIOS entry point. As a result, BIOS ends up bombarded with interrupts early on boot. The BIOS does not expect it since following a "normal" hardware cpu reset, all APIC LVT registers have the Mask bit (16) set and can't generate interrupts. For example, the version of Phoenix BIOS used by VMware enables interrupts for the first time before masking/clearing APIC LVT. The APIC Timer LVT register is still set up for a timer interrupt delivery with a high vector from the previous Linux incarnation (0xef in our case). The BIOS has not fully initialized its IDT at this point and the real mode gate for 0xef remains all zeros. Vector 0xef dispatches BIOS to address 0:0, BIOS takes a #GP and eventually hangs. machine_shutdown() does attempt to shut down APIC before jumping to BIOS, but it is ineffective" Signed-off-by: Zwane Mwaikambo Cc: "Seth, Rohit" Cc: Zachary Amsden Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/apic.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c index 7c724ff..496a2c9 100644 --- a/arch/i386/kernel/apic.c +++ b/arch/i386/kernel/apic.c @@ -559,14 +559,20 @@ void __devinit setup_local_APIC(void) * If Linux enabled the LAPIC against the BIOS default * disable it down before re-entering the BIOS on shutdown. * Otherwise the BIOS may get confused and not power-off. + * Additionally clear all LVT entries before disable_local_APIC + * for the case where Linux didn't enable the LAPIC. */ void lapic_shutdown(void) { - if (!cpu_has_apic || !enabled_via_apicbase) + if (!cpu_has_apic) return; local_irq_disable(); - disable_local_APIC(); + clear_local_APIC(); + + if (enabled_via_apicbase) + disable_local_APIC(); + local_irq_enable(); } -- 2.7.4