x86/apic: Fix restoring boot IRQ mode in reboot and kexec/kdump

This is a regression fix.

Before, to fix erratum AVR31, the following commit:

  522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")

... moved the lapic_shutdown() call to after disable_IO_APIC() in the reboot
and kexec/kdump code paths.

This introduced the following regression: disable_IO_APIC() not only clears
the IO-APIC, but it also restores boot IRQ mode by setting the
LAPIC/APIC/IMCR, calling lapic_shutdown() after disable_IO_APIC() will
disable LAPIC and ruin the possible virtual wire mode setting which
the code has been trying to do all along.

The consequence is that a KVM guest kernel always prints the warning below
during kexec/kdump as the kernel boots up:

  [    0.001000] WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1467 setup_local_APIC+0x228/0x330
  [    ........]
  [    0.001000] Call Trace:
  [    0.001000]  apic_bsp_setup+0x56/0x74
  [    0.001000]  x86_late_time_init+0x11/0x16
  [    0.001000]  start_kernel+0x3c9/0x486
  [    0.001000]  secondary_startup_64+0xa5/0xb0
  [    ........]
  [    0.001000] masked ExtINT on CPU#0

To fix this, just call clear_IO_APIC() to stop the IO-APIC where
disable_IO_APIC() was called, and call restore_boot_irq_mode() to
restore boot IRQ mode before a reboot or a kexec/kdump jump.

Signed-off-by: Baoquan He <[email protected]>
Reviewed-by: Eric W. Biederman <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Fixes: commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")
Link: http://lkml.kernel.org/r/[email protected]
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 10e74d4778a1c48925e8d9a72f185d925c9eae3a..1f6680427ff0ecd7813b9b9b356800acb1af1bc9 100644 (file)
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -199,9 +199,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 #ifdef CONFIG_X86_IO_APIC
        /* Prevent crash_kexec() from deadlocking on ioapic_lock. */
        ioapic_zap_locks();
-       disable_IO_APIC();
+       clear_IO_APIC();
 #endif
        lapic_shutdown();
+       restore_boot_irq_mode();
 #ifdef CONFIG_HPET_TIMER
        hpet_disable();
 #endif

diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 2126b9d27c3401e5ee518b490f8cb045fc0a29cd..725624b6c0c05cdc0c94175214a7ce796df47eee 100644 (file)
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -666,7 +666,7 @@ void native_machine_shutdown(void)
         * Even without the erratum, it still makes sense to quiet IO APIC
         * before disabling Local APIC.
         */
-       disable_IO_APIC();
+       clear_IO_APIC();
 #endif
 
 #ifdef CONFIG_SMP
@@ -680,6 +680,7 @@ void native_machine_shutdown(void)
 #endif
 
        lapic_shutdown();
+       restore_boot_irq_mode();
 
 #ifdef CONFIG_HPET_TIMER
        hpet_disable();