1 // SPDX-License-Identifier: GPL-2.0
3 * General MIPS MT support routines, usable in AP/SP and SMVP.
4 * Copyright (C) 2005 Mips Technologies, Inc
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 #include <asm/syscalls.h>
21 * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
23 cpumask_t mt_fpu_cpumask;
25 static int fpaff_threshold = -1;
26 unsigned long mt_fpemul_threshold;
29 * Replacement functions for the sys_sched_setaffinity() and
30 * sys_sched_getaffinity() system calls, so that we can integrate
31 * FPU affinity with the user's requested processor affinity.
32 * This code is 98% identical with the sys_sched_setaffinity()
33 * and sys_sched_getaffinity() system calls, and should be
34 * updated when kernel/sched/core.c changes.
38 * find_process_by_pid - find a process with a matching PID value.
39 * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
42 static inline struct task_struct *find_process_by_pid(pid_t pid)
44 return pid ? find_task_by_vpid(pid) : current;
48 * check the target process has a UID that matches the current process's
50 static bool check_same_owner(struct task_struct *p)
52 const struct cred *cred = current_cred(), *pcred;
56 pcred = __task_cred(p);
57 match = (uid_eq(cred->euid, pcred->euid) ||
58 uid_eq(cred->euid, pcred->uid));
64 * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
66 asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
67 unsigned long __user *user_mask_ptr)
69 cpumask_var_t cpus_allowed, new_mask, effective_mask;
70 struct thread_info *ti;
71 struct task_struct *p;
74 if (len < sizeof(new_mask))
77 if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
83 p = find_process_by_pid(pid);
90 /* Prevent p going away */
94 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
98 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
100 goto out_free_cpus_allowed;
102 if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
104 goto out_free_new_mask;
106 if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
111 retval = security_task_setscheduler(p);
115 /* Record new user-specified CPU set for future reference */
116 cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
119 /* Compute new global allowed CPU set if necessary */
120 ti = task_thread_info(p);
121 if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
122 cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
123 cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
124 retval = set_cpus_allowed_ptr(p, effective_mask);
126 cpumask_copy(effective_mask, new_mask);
127 clear_ti_thread_flag(ti, TIF_FPUBOUND);
128 retval = set_cpus_allowed_ptr(p, new_mask);
132 cpuset_cpus_allowed(p, cpus_allowed);
133 if (!cpumask_subset(effective_mask, cpus_allowed)) {
135 * We must have raced with a concurrent cpuset
136 * update. Just reset the cpus_allowed to the
137 * cpuset's cpus_allowed
139 cpumask_copy(new_mask, cpus_allowed);
144 free_cpumask_var(effective_mask);
146 free_cpumask_var(new_mask);
147 out_free_cpus_allowed:
148 free_cpumask_var(cpus_allowed);
156 * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
158 asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
159 unsigned long __user *user_mask_ptr)
161 unsigned int real_len;
162 cpumask_t allowed, mask;
164 struct task_struct *p;
166 real_len = sizeof(mask);
174 p = find_process_by_pid(pid);
177 retval = security_task_getscheduler(p);
181 cpumask_or(&allowed, &p->thread.user_cpus_allowed, p->cpus_ptr);
182 cpumask_and(&mask, &allowed, cpu_active_mask);
189 if (copy_to_user(user_mask_ptr, &mask, real_len))
195 static int __init fpaff_thresh(char *str)
197 get_option(&str, &fpaff_threshold);
200 __setup("fpaff=", fpaff_thresh);
203 * FPU Use Factor empirically derived from experiments on 34K
205 #define FPUSEFACTOR 2000
207 static __init int mt_fp_affinity_init(void)
209 if (fpaff_threshold >= 0) {
210 mt_fpemul_threshold = fpaff_threshold;
212 mt_fpemul_threshold =
213 (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
215 printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
216 mt_fpemul_threshold);
220 arch_initcall(mt_fp_affinity_init);