1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_VGTOD_H 3 #define _ASM_X86_VGTOD_H 4 5 #include <linux/compiler.h> 6 #include <linux/clocksource.h> 7 8 #ifdef BUILD_VDSO32_64 9 typedef u64 gtod_long_t; 10 #else 11 typedef unsigned long gtod_long_t; 12 #endif 13 /* 14 * vsyscall_gtod_data will be accessed by 32 and 64 bit code at the same time 15 * so be carefull by modifying this structure. 16 */ 17 struct vsyscall_gtod_data { 18 unsigned seq; 19 20 int vclock_mode; 21 u64 cycle_last; 22 u64 mask; 23 u32 mult; 24 u32 shift; 25 26 /* open coded 'struct timespec' */ 27 u64 wall_time_snsec; 28 gtod_long_t wall_time_sec; 29 gtod_long_t monotonic_time_sec; 30 u64 monotonic_time_snsec; 31 gtod_long_t wall_time_coarse_sec; 32 gtod_long_t wall_time_coarse_nsec; 33 gtod_long_t monotonic_time_coarse_sec; 34 gtod_long_t monotonic_time_coarse_nsec; 35 36 int tz_minuteswest; 37 int tz_dsttime; 38 }; 39 extern struct vsyscall_gtod_data vsyscall_gtod_data; 40 41 extern int vclocks_used; 42 static inline bool vclock_was_used(int vclock) 43 { 44 return READ_ONCE(vclocks_used) & (1 << vclock); 45 } 46 47 static inline unsigned gtod_read_begin(const struct vsyscall_gtod_data *s) 48 { 49 unsigned ret; 50 51 repeat: 52 ret = ACCESS_ONCE(s->seq); 53 if (unlikely(ret & 1)) { 54 cpu_relax(); 55 goto repeat; 56 } 57 smp_rmb(); 58 return ret; 59 } 60 61 static inline int gtod_read_retry(const struct vsyscall_gtod_data *s, 62 unsigned start) 63 { 64 smp_rmb(); 65 return unlikely(s->seq != start); 66 } 67 68 static inline void gtod_write_begin(struct vsyscall_gtod_data *s) 69 { 70 ++s->seq; 71 smp_wmb(); 72 } 73 74 static inline void gtod_write_end(struct vsyscall_gtod_data *s) 75 { 76 smp_wmb(); 77 ++s->seq; 78 } 79 80 #ifdef CONFIG_X86_64 81 82 #define VGETCPU_CPU_MASK 0xfff 83 84 static inline unsigned int __getcpu(void) 85 { 86 unsigned int p; 87 88 /* 89 * Load per CPU data from GDT. LSL is faster than RDTSCP and 90 * works on all CPUs. This is volatile so that it orders 91 * correctly wrt barrier() and to keep gcc from cleverly 92 * hoisting it out of the calling function. 93 * 94 * If RDPID is available, use it. 95 */ 96 alternative_io ("lsl %[p],%[seg]", 97 ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */ 98 X86_FEATURE_RDPID, 99 [p] "=a" (p), [seg] "r" (__PER_CPU_SEG)); 100 101 return p; 102 } 103 104 #endif /* CONFIG_X86_64 */ 105 106 #endif /* _ASM_X86_VGTOD_H */ 107