mips/kernel/mips-mt-fpaff.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * General MIPS MT support routines, usable in AP/SP and SMVP.
0004  * Copyright (C) 2005 Mips Technologies, Inc
0005  */
0006 #include <linux/cpu.h>
0007 #include <linux/cpuset.h>
0008 #include <linux/cpumask.h>
0009 #include <linux/delay.h>
0010 #include <linux/kernel.h>
0011 #include <linux/init.h>
0012 #include <linux/sched.h>
0013 #include <linux/sched/task.h>
0014 #include <linux/cred.h>
0015 #include <linux/security.h>
0016 #include <linux/types.h>
0017 #include <linux/uaccess.h>
0018
0019 /*
0020  * CPU mask used to set process affinity for MT VPEs/TCs with FPUs
0021  */
0022 cpumask_t mt_fpu_cpumask;
0023
0024 static int fpaff_threshold = -1;
0025 unsigned long mt_fpemul_threshold;
0026
0027 /*
0028  * Replacement functions for the sys_sched_setaffinity() and
0029  * sys_sched_getaffinity() system calls, so that we can integrate
0030  * FPU affinity with the user's requested processor affinity.
0031  * This code is 98% identical with the sys_sched_setaffinity()
0032  * and sys_sched_getaffinity() system calls, and should be
0033  * updated when kernel/sched/core.c changes.
0034  */
0035
0036 /*
0037  * find_process_by_pid - find a process with a matching PID value.
0038  * used in sys_sched_set/getaffinity() in kernel/sched/core.c, so
0039  * cloned here.
0040  */
0041 static inline struct task_struct *find_process_by_pid(pid_t pid)
0042 {
0043     return pid ? find_task_by_vpid(pid) : current;
0044 }
0045
0046 /*
0047  * check the target process has a UID that matches the current process's
0048  */
0049 static bool check_same_owner(struct task_struct *p)
0050 {
0051     const struct cred *cred = current_cred(), *pcred;
0052     bool match;
0053
0054     rcu_read_lock();
0055     pcred = __task_cred(p);
0056     match = (uid_eq(cred->euid, pcred->euid) ||
0057          uid_eq(cred->euid, pcred->uid));
0058     rcu_read_unlock();
0059     return match;
0060 }
0061
0062 /*
0063  * mipsmt_sys_sched_setaffinity - set the cpu affinity of a process
0064  */
0065 asmlinkage long mipsmt_sys_sched_setaffinity(pid_t pid, unsigned int len,
0066                       unsigned long __user *user_mask_ptr)
0067 {
0068     cpumask_var_t cpus_allowed, new_mask, effective_mask;
0069     struct thread_info *ti;
0070     struct task_struct *p;
0071     int retval;
0072
0073     if (len < sizeof(new_mask))
0074         return -EINVAL;
0075
0076     if (copy_from_user(&new_mask, user_mask_ptr, sizeof(new_mask)))
0077         return -EFAULT;
0078
0079     cpus_read_lock();
0080     rcu_read_lock();
0081
0082     p = find_process_by_pid(pid);
0083     if (!p) {
0084         rcu_read_unlock();
0085         cpus_read_unlock();
0086         return -ESRCH;
0087     }
0088
0089     /* Prevent p going away */
0090     get_task_struct(p);
0091     rcu_read_unlock();
0092
0093     if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
0094         retval = -ENOMEM;
0095         goto out_put_task;
0096     }
0097     if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
0098         retval = -ENOMEM;
0099         goto out_free_cpus_allowed;
0100     }
0101     if (!alloc_cpumask_var(&effective_mask, GFP_KERNEL)) {
0102         retval = -ENOMEM;
0103         goto out_free_new_mask;
0104     }
0105     if (!check_same_owner(p) && !capable(CAP_SYS_NICE)) {
0106         retval = -EPERM;
0107         goto out_unlock;
0108     }
0109
0110     retval = security_task_setscheduler(p);
0111     if (retval)
0112         goto out_unlock;
0113
0114     /* Record new user-specified CPU set for future reference */
0115     cpumask_copy(&p->thread.user_cpus_allowed, new_mask);
0116
0117  again:
0118     /* Compute new global allowed CPU set if necessary */
0119     ti = task_thread_info(p);
0120     if (test_ti_thread_flag(ti, TIF_FPUBOUND) &&
0121         cpumask_intersects(new_mask, &mt_fpu_cpumask)) {
0122         cpumask_and(effective_mask, new_mask, &mt_fpu_cpumask);
0123         retval = set_cpus_allowed_ptr(p, effective_mask);
0124     } else {
0125         cpumask_copy(effective_mask, new_mask);
0126         clear_ti_thread_flag(ti, TIF_FPUBOUND);
0127         retval = set_cpus_allowed_ptr(p, new_mask);
0128     }
0129
0130     if (!retval) {
0131         cpuset_cpus_allowed(p, cpus_allowed);
0132         if (!cpumask_subset(effective_mask, cpus_allowed)) {
0133             /*
0134              * We must have raced with a concurrent cpuset
0135              * update. Just reset the cpus_allowed to the
0136              * cpuset's cpus_allowed
0137              */
0138             cpumask_copy(new_mask, cpus_allowed);
0139             goto again;
0140         }
0141     }
0142 out_unlock:
0143     free_cpumask_var(effective_mask);
0144 out_free_new_mask:
0145     free_cpumask_var(new_mask);
0146 out_free_cpus_allowed:
0147     free_cpumask_var(cpus_allowed);
0148 out_put_task:
0149     put_task_struct(p);
0150     cpus_read_unlock();
0151     return retval;
0152 }
0153
0154 /*
0155  * mipsmt_sys_sched_getaffinity - get the cpu affinity of a process
0156  */
0157 asmlinkage long mipsmt_sys_sched_getaffinity(pid_t pid, unsigned int len,
0158                       unsigned long __user *user_mask_ptr)
0159 {
0160     unsigned int real_len;
0161     cpumask_t allowed, mask;
0162     int retval;
0163     struct task_struct *p;
0164
0165     real_len = sizeof(mask);
0166     if (len < real_len)
0167         return -EINVAL;
0168
0169     cpus_read_lock();
0170     rcu_read_lock();
0171
0172     retval = -ESRCH;
0173     p = find_process_by_pid(pid);
0174     if (!p)
0175         goto out_unlock;
0176     retval = security_task_getscheduler(p);
0177     if (retval)
0178         goto out_unlock;
0179
0180     cpumask_or(&allowed, &p->thread.user_cpus_allowed, p->cpus_ptr);
0181     cpumask_and(&mask, &allowed, cpu_active_mask);
0182
0183 out_unlock:
0184     rcu_read_unlock();
0185     cpus_read_unlock();
0186     if (retval)
0187         return retval;
0188     if (copy_to_user(user_mask_ptr, &mask, real_len))
0189         return -EFAULT;
0190     return real_len;
0191 }
0192
0193
0194 static int __init fpaff_thresh(char *str)
0195 {
0196     get_option(&str, &fpaff_threshold);
0197     return 1;
0198 }
0199 __setup("fpaff=", fpaff_thresh);
0200
0201 /*
0202  * FPU Use Factor empirically derived from experiments on 34K
0203  */
0204 #define FPUSEFACTOR 2000
0205
0206 static __init int mt_fp_affinity_init(void)
0207 {
0208     if (fpaff_threshold >= 0) {
0209         mt_fpemul_threshold = fpaff_threshold;
0210     } else {
0211         mt_fpemul_threshold =
0212             (FPUSEFACTOR * (loops_per_jiffy/(500000/HZ))) / HZ;
0213     }
0214     printk(KERN_DEBUG "FPU Affinity set after %ld emulations\n",
0215            mt_fpemul_threshold);
0216
0217     return 0;
0218 }
0219 arch_initcall(mt_fp_affinity_init);