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    SubjectRe: [tip:x86/urgent] x86, apic: Don't use logical-flat mode when CPU hotplug may exceed 8 CPUs
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    On Tue, 2010-02-09 at 10:47 -0800, Yinghai Lu wrote:
    > > #ifdef CONFIG_X86_32
    > > - if (num_processors > 8) {
    > > + if (num_possible_cpus() > 8) {
    >
    > for 32bit you can not use this function yet.
    > that only can be used after prefill_possible_map()

    Yinghai, Agreed. How about the appended patch? I tested and it works.
    Peter wants a small quick fix for this issue (to resolve the boot issue
    reported in the virtualization guest context) so that we can queue it
    for .33 and .32 kernels (as some distributions will be based on these
    kernels).

    Can you please Ack if it is ok?

    thanks,
    suresh
    ---

    From: Suresh Siddha <suresh.b.siddha@intel.com>
    Subject: x86, apic: Don't use logical-flat mode when CPU hotplug may exceed 8 CPUs

    We need to fall back from logical-flat APIC mode to physical-flat mode
    when we have more than 8 CPUs. However, in the presence of CPU
    hotplug(with bios listing not enabled but possible cpus as disabled cpus in
    MADT), we have to consider the number of possible CPUs rather than
    the number of current CPUs; otherwise we may cross the 8-CPU boundary
    when CPUs are added later.

    32bit apic code can use more cleanups (like the removal of vendor checks in
    32bit default_setup_apic_routing()) and more unifications with 64bit code.
    Yinghai has some patches in works already. This patch addresses the boot issue
    that is reported in the virtualization guest context.

    Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
    Acked-by: Shaohui Zheng <shaohui.zheng@intel.com>
    Cc: <stable@kernel.org>
    ---

    diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
    index 036d28a..0acbcdf 100644
    --- a/arch/x86/kernel/acpi/boot.c
    +++ b/arch/x86/kernel/acpi/boot.c
    @@ -1185,9 +1185,6 @@ static void __init acpi_process_madt(void)
    if (!error) {
    acpi_lapic = 1;

    -#ifdef CONFIG_X86_BIGSMP
    - generic_bigsmp_probe();
    -#endif
    /*
    * Parse MADT IO-APIC entries
    */
    @@ -1197,8 +1194,6 @@ static void __init acpi_process_madt(void)
    acpi_ioapic = 1;

    smp_found_config = 1;
    - if (apic->setup_apic_routing)
    - apic->setup_apic_routing();
    }
    }
    if (error == -EINVAL) {
    diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
    index a85f216..6e29b2a 100644
    --- a/arch/x86/kernel/apic/apic.c
    +++ b/arch/x86/kernel/apic/apic.c
    @@ -1641,9 +1641,7 @@ int __init APIC_init_uniprocessor(void)
    #endif

    enable_IR_x2apic();
    -#ifdef CONFIG_X86_64
    default_setup_apic_routing();
    -#endif

    verify_local_APIC();
    connect_bsp_APIC();
    @@ -1891,21 +1889,6 @@ void __cpuinit generic_processor_info(int apicid, int version)
    if (apicid > max_physical_apicid)
    max_physical_apicid = apicid;

    -#ifdef CONFIG_X86_32
    - if (num_processors > 8) {
    - switch (boot_cpu_data.x86_vendor) {
    - case X86_VENDOR_INTEL:
    - if (!APIC_XAPIC(version)) {
    - def_to_bigsmp = 0;
    - break;
    - }
    - /* If P4 and above fall through */
    - case X86_VENDOR_AMD:
    - def_to_bigsmp = 1;
    - }
    - }
    -#endif
    -
    #if defined(CONFIG_SMP) || defined(CONFIG_X86_64)
    early_per_cpu(x86_cpu_to_apicid, cpu) = apicid;
    early_per_cpu(x86_bios_cpu_apicid, cpu) = apicid;
    diff --git a/arch/x86/kernel/apic/probe_32.c b/arch/x86/kernel/apic/probe_32.c
    index 1a6559f..88e78ae 100644
    --- a/arch/x86/kernel/apic/probe_32.c
    +++ b/arch/x86/kernel/apic/probe_32.c
    @@ -54,6 +54,31 @@ late_initcall(print_ipi_mode);

    void default_setup_apic_routing(void)
    {
    + int version = apic_version[boot_cpu_physical_apicid];
    +
    + if (num_possible_cpus() > 8) {
    + switch (boot_cpu_data.x86_vendor) {
    + case X86_VENDOR_INTEL:
    + if (!APIC_XAPIC(version)) {
    + def_to_bigsmp = 0;
    + break;
    + }
    + /* If P4 and above fall through */
    + case X86_VENDOR_AMD:
    + def_to_bigsmp = 1;
    + }
    + }
    +
    +#ifdef CONFIG_X86_BIGSMP
    + generic_bigsmp_probe();
    +#endif
    +
    + if (apic->setup_apic_routing)
    + apic->setup_apic_routing();
    +}
    +
    +void setup_apic_flat_routing(void)
    +{
    #ifdef CONFIG_X86_IO_APIC
    printk(KERN_INFO
    "Enabling APIC mode: Flat. Using %d I/O APICs\n",
    @@ -103,7 +128,7 @@ struct apic apic_default = {
    .init_apic_ldr = default_init_apic_ldr,

    .ioapic_phys_id_map = default_ioapic_phys_id_map,
    - .setup_apic_routing = default_setup_apic_routing,
    + .setup_apic_routing = setup_apic_flat_routing,
    .multi_timer_check = NULL,
    .apicid_to_node = default_apicid_to_node,
    .cpu_to_logical_apicid = default_cpu_to_logical_apicid,
    diff --git a/arch/x86/kernel/apic/probe_64.c b/arch/x86/kernel/apic/probe_64.c
    index 450fe20..83e9be4 100644
    --- a/arch/x86/kernel/apic/probe_64.c
    +++ b/arch/x86/kernel/apic/probe_64.c
    @@ -67,7 +67,7 @@ void __init default_setup_apic_routing(void)
    }
    #endif

    - if (apic == &apic_flat && num_processors > 8)
    + if (apic == &apic_flat && num_possible_cpus() > 8)
    apic = &apic_physflat;

    printk(KERN_INFO "Setting APIC routing to %s\n", apic->name);
    diff --git a/arch/x86/kernel/mpparse.c b/arch/x86/kernel/mpparse.c
    index 40b54ce..a2c1edd 100644
    --- a/arch/x86/kernel/mpparse.c
    +++ b/arch/x86/kernel/mpparse.c
    @@ -359,13 +359,6 @@ static int __init smp_read_mpc(struct mpc_table *mpc, unsigned early)
    x86_init.mpparse.mpc_record(1);
    }

    -#ifdef CONFIG_X86_BIGSMP
    - generic_bigsmp_probe();
    -#endif
    -
    - if (apic->setup_apic_routing)
    - apic->setup_apic_routing();
    -
    if (!num_processors)
    printk(KERN_ERR "MPTABLE: no processors registered!\n");
    return num_processors;
    diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    index b2ebcba..c08829a 100644
    --- a/arch/x86/kernel/smpboot.c
    +++ b/arch/x86/kernel/smpboot.c
    @@ -1087,9 +1087,7 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
    set_cpu_sibling_map(0);

    enable_IR_x2apic();
    -#ifdef CONFIG_X86_64
    default_setup_apic_routing();
    -#endif

    if (smp_sanity_check(max_cpus) < 0) {
    printk(KERN_INFO "SMP disabled\n");



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