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linux-next/arch/x86/include/asm/topology.h
Giovanni Gherdovich e2b0d619b4 x86, sched: check for counters overflow in frequency invariant accounting 
The product mcnt * arch_max_freq_ratio can overflows u64.

For context, a large value for arch_max_freq_ratio would be 5000,
corresponding to a turbo_freq/base_freq ratio of 5 (normally it's more like
1500-2000). A large increment frequency for the MPERF counter would be 5GHz
(the base clock of all CPUs on the market today is less than that). With
these figures, a CPU would need to go without a scheduler tick for around 8
days for the u64 overflow to happen. It is unlikely, but the check is
warranted.

Under similar conditions, the difference acnt of two consecutive APERF
readings can overflow as well.

In these circumstances is appropriate to disable frequency invariant
accounting: the feature relies on measures of the clock frequency done at
every scheduler tick, which need to be "fresh" to be at all meaningful.

A note on i386: prior to version 5.1, the GCC compiler didn't have the
builtin function __builtin_mul_overflow. In these GCC versions the macro
check_mul_overflow needs __udivdi3() to do (u64)a/b, which the kernel
doesn't provide. For this reason this change fails to build on i386 if
GCC<5.1, and we protect the entire frequency invariant code behind
CONFIG_X86_64 (special thanks to "kbuild test robot" <lkp@intel.com>).

Fixes: 1567c3e346 ("x86, sched: Add support for frequency invariance")
Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/20200531182453.15254-2-ggherdovich@suse.cz
2020-06-15 14:10:02 +02:00

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/*
* Written by: Matthew Dobson, IBM Corporation
*
* Copyright (C) 2002, IBM Corp.
*
* All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
* Send feedback to <colpatch@us.ibm.com>
*/
#ifndef _ASM_X86_TOPOLOGY_H
#define _ASM_X86_TOPOLOGY_H
/*
* to preserve the visibility of NUMA_NO_NODE definition,
* moved to there from here. May be used independent of
* CONFIG_NUMA.
*/
#include <linux/numa.h>
#ifdef CONFIG_NUMA
#include <linux/cpumask.h>
#include <asm/mpspec.h>
#include <asm/percpu.h>
/* Mappings between logical cpu number and node number */
DECLARE_EARLY_PER_CPU(int, x86_cpu_to_node_map);
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
/*
* override generic percpu implementation of cpu_to_node
*/
extern int __cpu_to_node(int cpu);
#define cpu_to_node __cpu_to_node
extern int early_cpu_to_node(int cpu);
#else /* !CONFIG_DEBUG_PER_CPU_MAPS */
/* Same function but used if called before per_cpu areas are setup */
static inline int early_cpu_to_node(int cpu)
{
return early_per_cpu(x86_cpu_to_node_map, cpu);
}
#endif /* !CONFIG_DEBUG_PER_CPU_MAPS */
/* Mappings between node number and cpus on that node. */
extern cpumask_var_t node_to_cpumask_map[MAX_NUMNODES];
#ifdef CONFIG_DEBUG_PER_CPU_MAPS
extern const struct cpumask *cpumask_of_node(int node);
#else
/* Returns a pointer to the cpumask of CPUs on Node 'node'. */
static inline const struct cpumask *cpumask_of_node(int node)
{
return node_to_cpumask_map[node];
}
#endif
extern void setup_node_to_cpumask_map(void);
#define pcibus_to_node(bus) __pcibus_to_node(bus)
extern int __node_distance(int, int);
#define node_distance(a, b) __node_distance(a, b)
#else /* !CONFIG_NUMA */
static inline int numa_node_id(void)
{
return 0;
}
/*
* indicate override:
*/
#define numa_node_id numa_node_id
static inline int early_cpu_to_node(int cpu)
{
return 0;
}
static inline void setup_node_to_cpumask_map(void) { }
#endif
#include <asm-generic/topology.h>
extern const struct cpumask *cpu_coregroup_mask(int cpu);
#define topology_logical_package_id(cpu) (cpu_data(cpu).logical_proc_id)
#define topology_physical_package_id(cpu) (cpu_data(cpu).phys_proc_id)
#define topology_logical_die_id(cpu) (cpu_data(cpu).logical_die_id)
#define topology_die_id(cpu) (cpu_data(cpu).cpu_die_id)
#define topology_core_id(cpu) (cpu_data(cpu).cpu_core_id)
#ifdef CONFIG_SMP
#define topology_die_cpumask(cpu) (per_cpu(cpu_die_map, cpu))
#define topology_core_cpumask(cpu) (per_cpu(cpu_core_map, cpu))
#define topology_sibling_cpumask(cpu) (per_cpu(cpu_sibling_map, cpu))
extern unsigned int __max_logical_packages;
#define topology_max_packages() (__max_logical_packages)
extern unsigned int __max_die_per_package;
static inline int topology_max_die_per_package(void)
{
return __max_die_per_package;
}
extern int __max_smt_threads;
static inline int topology_max_smt_threads(void)
{
return __max_smt_threads;
}
int topology_update_package_map(unsigned int apicid, unsigned int cpu);
int topology_update_die_map(unsigned int dieid, unsigned int cpu);
int topology_phys_to_logical_pkg(unsigned int pkg);
int topology_phys_to_logical_die(unsigned int die, unsigned int cpu);
bool topology_is_primary_thread(unsigned int cpu);
bool topology_smt_supported(void);
#else
#define topology_max_packages() (1)
static inline int
topology_update_package_map(unsigned int apicid, unsigned int cpu) { return 0; }
static inline int
topology_update_die_map(unsigned int dieid, unsigned int cpu) { return 0; }
static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
static inline int topology_phys_to_logical_die(unsigned int die,
unsigned int cpu) { return 0; }
static inline int topology_max_die_per_package(void) { return 1; }
static inline int topology_max_smt_threads(void) { return 1; }
static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }
static inline bool topology_smt_supported(void) { return false; }
#endif
static inline void arch_fix_phys_package_id(int num, u32 slot)
{
}
struct pci_bus;
int x86_pci_root_bus_node(int bus);
void x86_pci_root_bus_resources(int bus, struct list_head *resources);
extern bool x86_topology_update;
#ifdef CONFIG_SCHED_MC_PRIO
#include <asm/percpu.h>
DECLARE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
extern unsigned int __read_mostly sysctl_sched_itmt_enabled;
/* Interface to set priority of a cpu */
void sched_set_itmt_core_prio(int prio, int core_cpu);
/* Interface to notify scheduler that system supports ITMT */
int sched_set_itmt_support(void);
/* Interface to notify scheduler that system revokes ITMT support */
void sched_clear_itmt_support(void);
#else /* CONFIG_SCHED_MC_PRIO */
#define sysctl_sched_itmt_enabled 0
static inline void sched_set_itmt_core_prio(int prio, int core_cpu)
{
}
static inline int sched_set_itmt_support(void)
{
return 0;
}
static inline void sched_clear_itmt_support(void)
{
}
#endif /* CONFIG_SCHED_MC_PRIO */
#if defined(CONFIG_SMP) && defined(CONFIG_X86_64)
#include <asm/cpufeature.h>
DECLARE_STATIC_KEY_FALSE(arch_scale_freq_key);
#define arch_scale_freq_invariant() static_branch_likely(&arch_scale_freq_key)
DECLARE_PER_CPU(unsigned long, arch_freq_scale);
static inline long arch_scale_freq_capacity(int cpu)
{
return per_cpu(arch_freq_scale, cpu);
}
#define arch_scale_freq_capacity arch_scale_freq_capacity
extern void arch_scale_freq_tick(void);
#define arch_scale_freq_tick arch_scale_freq_tick
extern void arch_set_max_freq_ratio(bool turbo_disabled);
#else
static inline void arch_set_max_freq_ratio(bool turbo_disabled)
{
}
#endif
#endif /* _ASM_X86_TOPOLOGY_H */
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