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  */
  22 cpumask_t mt_fpu_cpumask;
  23
  24 static int fpaff_threshold = -1;
  25 unsigned 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  */
  41 static 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  */
  49 static 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  */
  65 asmlinkage 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         }
 142 out_unlock:
 143         free_cpumask_var(effective_mask);
 144 out_free_new_mask:
 145         free_cpumask_var(new_mask);
 146 out_free_cpus_allowed:
 147         free_cpumask_var(cpus_allowed);
 148 out_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  */
 157 asmlinkage 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
 183 out_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
 194 static 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
 206 static __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 }
 219 arch_initcall(mt_fp_affinity_init);