Commit 5989cd6a authored Aug 04, 2010 by Eric W. Biederman Committed by H. Peter Anvin Aug 05, 2010

x86, apic: Map the local apic when parsing the MP table.

This fixes a regression in 2.6.35 from 2.6.34, that is
present for select models of Intel cpus when people are
using an MP table.

The commit cf7500c0
"x86, ioapic: In mpparse use mp_register_ioapic" started
calling mp_register_ioapic from MP_ioapic_info.  An extremely
simple change that was obviously correct.  Unfortunately
mp_register_ioapic did just a little more than the previous
hand crafted code and so we gained this call path.

The problem call path is:
MP_ioapic_info()
  mp_register_ioapic()
   io_apic_unique_id()
     io_apic_get_unique_id()
       get_physical_broadcast()
         modern_apic()
           lapic_get_version()
             apic_read(APIC_LVR)

Which turned out to be a problem because the local apic
was not mapped, at that point, unlike the similar point
in the ACPI parsing code.

This problem is fixed by mapping the local apic when
parsing the mptable as soon as we reasonably can.

Looking at the number of places we setup the fixmap for
the local apic, I see some serious simplification opportunities.
For the moment except for not duplicating the setting up of the
fixmap in init_apic_mappings, I have not acted on them.

The regression from 2.6.34 is tracked in bug
https://bugzilla.kernel.org/show_bug.cgi?id=16173



Cc: <stable@kernel.org> 2.6.35
Reported-by: David Hill <hilld@binarystorm.net>
Reported-by: Tvrtko Ursulin <tvrtko.ursulin@sophos.com>
Tested-by: Tvrtko Ursulin <tvrtko.ursulin@sophos.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
LKML-Reference: <m1eiee86jg.fsf_-_@fess.ebiederm.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

parent 113fc5a6

arch/x86/kernel/apic/apic.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1606,7 +1606,7 @@ void __init init_apic_mappings(void)
		* acpi lapic path already maps that address in
		* acpi_register_lapic_address()
		*/
		if (!acpi_lapic)
		if (!acpi_lapic && !smp_found_config)
		set_fixmap_nocache(FIX_APIC_BASE, apic_phys);

		apic_printk(APIC_VERBOSE, "mapped APIC to %08lx (%08lx)\n",

arch/x86/kernel/mpparse.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -274,6 +274,18 @@ static void __init smp_dump_mptable(struct mpc_table mpc, unsigned char mpt)

		void __init default_smp_read_mpc_oem(struct mpc_table *mpc) { }

		static void __init smp_register_lapic_address(unsigned long address)
		{
		mp_lapic_addr = address;

		set_fixmap_nocache(FIX_APIC_BASE, address);
		if (boot_cpu_physical_apicid == -1U) {
		boot_cpu_physical_apicid = read_apic_id();
		apic_version[boot_cpu_physical_apicid] =
		GET_APIC_VERSION(apic_read(APIC_LVR));
		}
		}

		static int __init smp_read_mpc(struct mpc_table *mpc, unsigned early)
		{
		char str[16];
		@@ -295,6 +307,10 @@ static int __init smp_read_mpc(struct mpc_table *mpc, unsigned early)
		if (early)
		return 1;

		/* Initialize the lapic mapping */
		if (!acpi_lapic)
		smp_register_lapic_address(mpc->lapic);

		if (mpc->oemptr)
		x86_init.mpparse.smp_read_mpc_oem(mpc);

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