[PATCH] Disable APIC on reboot.

davej_at_redhat.com
Date: 08/11/03

  • Next message: David Woodhouse: "Re: compiling external kernel modules (comedi.org)" 
    To: torvalds@transmeta.com
Date:	Mon, 11 Aug 2003 14:40:24 +0100

    Forward port of a patch from Felix [surname mangled by MTA] <fxkuehl@gmx.de>

    Original mail:-

    when I reboot my laptop the BIOS complains about a keyboard controller
    failure and timer interrupts not working. On the BIOS password screen
    the keyboard doesn't work. If I disable the BIOS password the system
    hangs a bit later on the POST screen. I tried all reboot methods via the
    kernel command line without success. I saw this problem with Debian
    Woody's precompiled 2.4.18 kernel, self compiled Debian 2.4.20 sources
    and Linux 2.4.21-rc1+ACPI patch. This problem only occurs if
    CONFIG_X86_LOCAL_APIC is enabled. With CONFIG_X86_LOCAL_APIC disabled it
    reboots just fine.

    My guess is that it's a BIOS bug as I've never had this problem on other
    machines before. I found a workaround: disable the local APIC before
    rebooting. I don't really know how it works. Just calling
    disable_local_APIC wasn't enough, so I copied a bit more code from
    apic_pm_suspend (arch/i386/kernel/apic.c:465) to machine_restart
    (arch/i386/kernel/process.c:369). I'm pretty sure that this is not the
    proper way to do it but it works here. A patch against 2.4.21-rc1 can be
    found at the end of this email.

    diff -urpN --exclude-from=/home/davej/.exclude bk-linus/arch/i386/kernel/reboot.c linux-2.5/arch/i386/kernel/reboot.c
    --- bk-linus/arch/i386/kernel/reboot.c 2003-05-13 11:51:12.000000000 +0100
    +++ linux-2.5/arch/i386/kernel/reboot.c 2003-07-16 02:54:29.000000000 +0100
    @@ -8,6 +8,7 @@
     #include <linux/interrupt.h>
     #include <linux/mc146818rtc.h>
     #include <asm/uaccess.h>
    +#include <asm/apic.h>
     #include "mach_reboot.h"
     
     /*
    @@ -250,6 +251,19 @@ void machine_restart(char * __unused)
              */
             smp_send_stop();
             disable_IO_APIC();
    +#else
    +#ifdef CONFIG_X86_LOCAL_APIC
    + {
    + unsigned int l, h;
    +
    + local_irq_disable();
    + disable_local_APIC();
    + rdmsr(MSR_IA32_APICBASE, l, h);
    + l &= ~MSR_IA32_APICBASE_ENABLE;
    + wrmsr(MSR_IA32_APICBASE, l, h);
    + local_irq_enable();
    +}
    +#endif
     #endif
     
             if(!reboot_thru_bios) {
    -
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