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    Subject[PATCH 3/3 v2] x86/smpboot: Fix __max_logical_packages estimate
    Date
    A system booted with a small number of cores enabled per package
    panics because the estimate of __max_logical_packages is too low.
    This occurs when the total number of active cores across all packages
    is less than the maximum core count for a single package.

    ie) On a 4 package system with 20 cores/package where only 4 cores
    are enabled on each package, the value of __max_logical_packages is
    calculated as DIV_ROUND_UP(16 / 20) = 1 and not 4.

    Calculate __max_logical_packages after the cpu enumeration has completed.
    Use the boot cpu's data to extrapolate the number of packages.

    Signed-off-by: Prarit Bhargava <prarit@redhat.com>
    ---
    arch/x86/kernel/smpboot.c | 57 +++++++++--------------------------------------
    1 file changed, 10 insertions(+), 47 deletions(-)

    diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    index a6e9bd971b91..1b86ba57ab1a 100644
    --- a/arch/x86/kernel/smpboot.c
    +++ b/arch/x86/kernel/smpboot.c
    @@ -288,12 +288,6 @@ int topology_update_package_map(unsigned int pkg, unsigned int cpu)
    if (new >= 0)
    goto found;

    - if (logical_packages >= __max_logical_packages) {
    - pr_warn("Package %u of CPU %u exceeds BIOS package data %u.\n",
    - logical_packages, cpu, __max_logical_packages);
    - return -ENOSPC;
    - }
    -
    new = logical_packages++;
    if (new != pkg)
    pr_info("CPU %u Converting physical %u to logical package %u\n",
    @@ -325,46 +319,6 @@ int topology_phys_to_logical_pkg(unsigned int phys_pkg)
    }
    EXPORT_SYMBOL(topology_phys_to_logical_pkg);

    -static void __init smp_init_package_map(struct cpuinfo_x86 *c, unsigned int cpu)
    -{
    - unsigned int ncpus;
    -
    - /*
    - * Today neither Intel nor AMD support heterogenous systems. That
    - * might change in the future....
    - *
    - * While ideally we'd want '* smp_num_siblings' in the below @ncpus
    - * computation, this won't actually work since some Intel BIOSes
    - * report inconsistent HT data when they disable HT.
    - *
    - * In particular, they reduce the APIC-IDs to only include the cores,
    - * but leave the CPUID topology to say there are (2) siblings.
    - * This means we don't know how many threads there will be until
    - * after the APIC enumeration.
    - *
    - * By not including this we'll sometimes over-estimate the number of
    - * logical packages by the amount of !present siblings, but this is
    - * still better than MAX_LOCAL_APIC.
    - *
    - * We use total_cpus not nr_cpu_ids because nr_cpu_ids can be limited
    - * on the command line leading to a similar issue as the HT disable
    - * problem because the hyperthreads are usually enumerated after the
    - * primary cores.
    - */
    - ncpus = boot_cpu_data.x86_max_cores;
    - if (!ncpus) {
    - pr_warn("x86_max_cores == zero !?!?");
    - ncpus = 1;
    - }
    -
    - __max_logical_packages = DIV_ROUND_UP(total_cpus, ncpus);
    - pr_info("Max logical packages: %u\n", __max_logical_packages);
    -
    - logical_packages = 0;
    -
    - topology_update_package_map(c->phys_proc_id, cpu);
    -}
    -
    void __init smp_store_boot_cpu_info(void)
    {
    int id = 0; /* CPU 0 */
    @@ -372,7 +326,7 @@ void __init smp_store_boot_cpu_info(void)

    *c = boot_cpu_data;
    c->cpu_index = id;
    - smp_init_package_map(c, id);
    + topology_update_package_map(c->phys_proc_id, id);
    }

    /*
    @@ -1372,7 +1326,16 @@ void __init native_smp_prepare_boot_cpu(void)

    void __init native_smp_cpus_done(unsigned int max_cpus)
    {
    + int ncpus;
    +
    pr_debug("Boot done\n");
    + /*
    + * Today neither Intel nor AMD support heterogenous systems so
    + * extrapolate the boot cpu's data to all packages.
    + */
    + ncpus = cpu_data(0).booted_cores * smp_num_siblings;
    + __max_logical_packages = DIV_ROUND_UP(nr_cpu_ids, ncpus);
    + pr_info("Max logical packages: %u\n", __max_logical_packages);

    if (x86_has_numa_in_package)
    set_sched_topology(x86_numa_in_package_topology);
    --
    1.8.5.5
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