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Commit be0d03f1 authored by Vivek Goyal's avatar Vivek Goyal Committed by Linus Torvalds
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[PATCH] i386 kdump boot cpu physical apicid fix 



o Kdump second kernel boot fails after a system crash if second kernel
  is UP and acpi=off and if crash occurred on a non-boot cpu.

o Issue here is that MP tables report boot cpu lapic id as 0 but second
  kernel is booting on a different processor and MP table data is stale
  in this context. Hence apic_id_registered() check fails in setup_local_APIC()
  when called from APIC_init_uniprocessor().

o Problem is not seen if ACPI is enabled as in that case
  boot_cpu_physical_apicid is read from the LAPIC.

o Problem is not seen with SMP kernels as well because in this case also
  boot_cpu_physical_apicid is read from LAPIC. (smp_boot_cpus()).

o The problem is fixed by reading boot_cpu_physical_apicid from LAPIC
  if it is a UP kernel and CRASH_DUMP is enabled.

Signed-off-by: default avatarVivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 5daa3ba0

arch/i386/kernel/apic.c

+8 −0
Original line number Diff line number Diff line
@@ -1341,6 +1341,14 @@ int __init APIC_init_uniprocessor (void) 


	connect_bsp_APIC();



	/*

	 * Hack: In case of kdump, after a crash, kernel might be booting

	 * on a cpu with non-zero lapic id. But boot_cpu_physical_apicid

	 * might be zero if read from MP tables. Get it from LAPIC.

	 */

#ifdef CONFIG_CRASH_DUMP

	boot_cpu_physical_apicid = GET_APIC_ID(apic_read(APIC_ID));

#endif

	phys_cpu_present_map = physid_mask_of_physid(boot_cpu_physical_apicid);



	setup_local_APIC();