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Subject[PATCH 3/3] 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.

eg) 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 ab588ff56650..51581a38543a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -287,12 +287,6 @@ 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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