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From: Yinghai Lu on 4 Aug 2010 18:00
On 08/04/2010 01:30 PM, Eric W. Biederman wrote:
>
> 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 cf7500c0ea133d66f8449d86392d83f840102632
> "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(a)kernel.org
> Reported-by: David Hill <hilld(a)binarystorm.net>
> Reported-by: Tvrtko Ursulin <tvrtko.ursulin(a)sophos.com>
> Tested-by: Tvrtko Ursulin <tvrtko.ursulin(a)sophos.com>
> Signed-off-by: Eric W. Biederman <ebiederm(a)xmission.com>
> ---
> arch/x86/kernel/apic/apic.c | 2 +-
> arch/x86/kernel/mpparse.c | 16 ++++++++++++++++
> 2 files changed, 17 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
> index a96489e..c07e513 100644
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -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",
> diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
> index d86dbf7..d7b6f7f 100644
> --- a/arch/x86/kernel/mpparse.c
> +++ b/arch/x86/kernel/mpparse.c
> @@ -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);
>

Acked-by: Yinghai Lu <yinghai(a)kernel.org>

will send out another two patches on top this one for cleanup.

Yinghai
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