LXR linux/arch/mips/kernel/mips-mt-fpaff.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * General MIPS MT support routines, usable in AP/SP and SMVP.
   4 * Copyright (C) 2005 Mips Technologies, Inc
   5 */
   6#include <linux/cpu.h>
   7#include <linux/cpuset.h>
   8#include <linux/cpumask.h>
   9#include <linux/delay.h>
  10#include <linux/kernel.h>
  11#include <linux/init.h>
  12#include <linux/sched.h>
  13#include <linux/sched/task.h>
  14#include <linux/cred.h>
  15#include <linux/security.h>
  16#include <linux/types.h>
  17#include <linux/uaccess.h>
  18
  19/*
  20 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
  21 */
  22cpumask_t mt_fpu_cpumask;
  23
  24static int fpaff_threshold = -1;
  25unsigned long mt_fpemul_threshold;
  26
  27/*
  28 * Replacement functions for the sys_sched_setaffinity() and
  29 * sys_sched_getaffinity() system calls, so that we can integrate
  30 * FPU affinity with the user's requested processor affinity.
  31 * This code is 98% identical with the sys_sched_setaffinity()
  32 * and sys_sched_getaffinity() system calls, and should be
  33 * updated when kernel/sched/core.c changes.
  34 */
  35
  36/*
  37 * find_process_by_pid - find a process with a matching PID value.
  38 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
  39 * cloned here.
  40 */
  41static inline struct task_struct *find_process_by_pid(pid_t pid)
  42{
  43        return pid ? find_task_by_vpid(pid) : current;
  44}
  45
  46/*
  47 * check the target process has a UID that matches the current process's
  48 */
  49static bool check_same_owner(struct task_struct *p)
  50{
  51        const struct cred *cred = current_cred(), *pcred;
  52        bool match;
  53
  54        rcu_read_lock();
  55        pcred = __task_cred(p);
  56        match = (uid_eq(cred->euid, pcred->euid) ||
  57                 uid_eq(cred->euid, pcred->uid));
  58        rcu_read_unlock();
  59        return match;
  60}
  61
  62/*
  63 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
  64 */
  65asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
  66                                      unsigned long __user *user_mask_ptr)
  67{
  68        cpumask_var_t cpus_allowed, new_mask, effective_mask;
  69        struct thread_info *ti;
  70        struct task_struct *p;
  71        int retval;
  72
  73        if (len < sizeof(new_mask))
  74                return -EINVAL;
  75
  76        if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
  77                return -EFAULT;
  78
  79        get_online_cpus();
  80        rcu_read_lock();
  81
  82        p = find_process_by_pid(pid);
  83        if (!p) {
  84                rcu_read_unlock();
  85                put_online_cpus();
  86                return -ESRCH;
  87        }
  88
  89        /* Prevent p going away */
  90        get_task_struct(p);
  91        rcu_read_unlock();
  92
  93        if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
  94                retval = -ENOMEM;
  95                goto out_put_task;
  96        }
  97        if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
  98                retval = -ENOMEM;
  99                goto out_free_cpus_allowed;
 100        }
 101        if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
 102                retval = -ENOMEM;
 103                goto out_free_new_mask;
 104        }
 105        if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
 106                retval = -EPERM;
 107                goto out_unlock;
 108        }
 109
 110        retval = security_task_setscheduler(p);
 111        if (retval)
 112                goto out_unlock;
 113
 114        /* Record new user-specified CPU set for future reference */
 115        cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
 116
 117 again:
 118        /* Compute new global allowed CPU set if necessary */
 119        ti = task_thread_info(p);
 120        if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
 121            cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
 122                cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
 123                retval = set_cpus_allowed_ptr(p, effective_mask);
 124        } else {
 125                cpumask_copy(effective_mask, new_mask);
 126                clear_ti_thread_flag(ti, TIF_FPUBOUND);
 127                retval = set_cpus_allowed_ptr(p, new_mask);
 128        }
 129
 130        if (!retval) {
 131                cpuset_cpus_allowed(p, cpus_allowed);
 132                if (!cpumask_subset(effective_mask, cpus_allowed)) {
 133                        /*
 134                         * We must have raced with a concurrent cpuset
 135                         * update. Just reset the cpus_allowed to the
 136                         * cpuset's cpus_allowed
 137                         */
 138                        cpumask_copy(new_mask, cpus_allowed);
 139                        goto again;
 140                }
 141        }
 142out_unlock:
 143        free_cpumask_var(effective_mask);
 144out_free_new_mask:
 145        free_cpumask_var(new_mask);
 146out_free_cpus_allowed:
 147        free_cpumask_var(cpus_allowed);
 148out_put_task:
 149        put_task_struct(p);
 150        put_online_cpus();
 151        return retval;
 152}
 153
 154/*
 155 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
 156 */
 157asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
 158                                      unsigned long __user *user_mask_ptr)
 159{
 160        unsigned int real_len;
 161        cpumask_t allowed, mask;
 162        int retval;
 163        struct task_struct *p;
 164
 165        real_len = sizeof(mask);
 166        if (len < real_len)
 167                return -EINVAL;
 168
 169        get_online_cpus();
 170        rcu_read_lock();
 171
 172        retval = -ESRCH;
 173        p = find_process_by_pid(pid);
 174        if (!p)
 175                goto out_unlock;
 176        retval = security_task_getscheduler(p);
 177        if (retval)
 178                goto out_unlock;
 179
 180        cpumask_or(&allowed, &p->thread.user_cpus_allowed, p->cpus_ptr);
 181        cpumask_and(&mask, &allowed, cpu_active_mask);
 182
 183out_unlock:
 184        rcu_read_unlock();
 185        put_online_cpus();
 186        if (retval)
 187                return retval;
 188        if (copy_to_user(user_mask_ptr, &mask, real_len))
 189                return -EFAULT;
 190        return real_len;
 191}
 192
 193
 194static int __init fpaff_thresh(char *str)
 195{
 196        get_option(&str, &fpaff_threshold);
 197        return 1;
 198}
 199__setup("fpaff=", fpaff_thresh);
 200
 201/*
 202 * FPU Use Factor empirically derived from experiments on 34K
 203 */
 204#define FPUSEFACTOR 2000
 205
 206static __init int mt_fp_affinity_init(void)
 207{
 208        if (fpaff_threshold >= 0) {
 209                mt_fpemul_threshold = fpaff_threshold;
 210        } else {
 211                mt_fpemul_threshold =
 212                        (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
 213        }
 214        printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
 215               mt_fpemul_threshold);
 216
 217        return 0;
 218}
 219arch_initcall(mt_fp_affinity_init);
 220