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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:

  522e664644 ("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 <bhe@redhat.com>
Reviewed-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: douly.fnst@cn.fujitsu.com
Cc: joro@8bytes.org
Cc: prarit@redhat.com
Cc: stable@vger.kernel.org
Cc: uobergfe@redhat.com
Fixes: commit 522e664644 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")
Link: http://lkml.kernel.org/r/20180214054656.3780-4-bhe@redhat.com
[ Rewrote the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Baoquan He 2018-02-14 13:46:53 +08:00 committed by Ingo Molnar
parent 3c9e76dbea
commit 339b2ae0cd
2 changed files with 4 additions and 2 deletions
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3
arch/x86/kernel/crash.c
View File

@ -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

3
arch/x86/kernel/reboot.c
View File

@ -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();