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Commit b4c0a732 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by Thomas Gleixner
Browse files

x86/smpboot: Fix __max_logical_packages estimate 



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. e.g.:

  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: default avatarPrarit Bhargava <prarit@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Kan Liang <kan.liang@intel.com>
Cc: He Chen <he.chen@linux.intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Piotr Luc <piotr.luc@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arvind Yadav <arvind.yadav.cs@gmail.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Link: https://lkml.kernel.org/r/20171114124257.22013-4-prarit@redhat.com
parent 30bb9811

arch/x86/kernel/smpboot.c

+10 −45
Original line number Diff line number Diff line
@@ -310,12 +310,6 @@ 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",
@@ -326,44 +320,6 @@ int topology_update_package_map(unsigned int pkg, unsigned int cpu) 
	return 0;

}



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);



	topology_update_package_map(c->phys_proc_id, cpu);

}



void __init smp_store_boot_cpu_info(void)

{

	int id = 0; /* CPU 0 */
@@ -371,7 +327,7 @@ 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);

	c->initialized = true;

}
@@ -1341,7 +1297,16 @@ 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);