xref: /openbmc/linux/arch/x86/include/asm/pvclock.h (revision b34e08d5)
1 #ifndef _ASM_X86_PVCLOCK_H
2 #define _ASM_X86_PVCLOCK_H
3 
4 #include <linux/clocksource.h>
5 #include <asm/pvclock-abi.h>
6 
7 /* some helper functions for xen and kvm pv clock sources */
8 cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
9 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
10 void pvclock_set_flags(u8 flags);
11 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
12 void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
13 			    struct pvclock_vcpu_time_info *vcpu,
14 			    struct timespec *ts);
15 void pvclock_resume(void);
16 
17 void pvclock_touch_watchdogs(void);
18 
19 /*
20  * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
21  * yielding a 64-bit result.
22  */
23 static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
24 {
25 	u64 product;
26 #ifdef __i386__
27 	u32 tmp1, tmp2;
28 #else
29 	ulong tmp;
30 #endif
31 
32 	if (shift < 0)
33 		delta >>= -shift;
34 	else
35 		delta <<= shift;
36 
37 #ifdef __i386__
38 	__asm__ (
39 		"mul  %5       ; "
40 		"mov  %4,%%eax ; "
41 		"mov  %%edx,%4 ; "
42 		"mul  %5       ; "
43 		"xor  %5,%5    ; "
44 		"add  %4,%%eax ; "
45 		"adc  %5,%%edx ; "
46 		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
47 		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
48 #elif defined(__x86_64__)
49 	__asm__ (
50 		"mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
51 		: [lo]"=a"(product),
52 		  [hi]"=d"(tmp)
53 		: "0"(delta),
54 		  [mul_frac]"rm"((u64)mul_frac));
55 #else
56 #error implement me!
57 #endif
58 
59 	return product;
60 }
61 
62 static __always_inline
63 u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
64 {
65 	u64 delta = __native_read_tsc() - src->tsc_timestamp;
66 	return pvclock_scale_delta(delta, src->tsc_to_system_mul,
67 				   src->tsc_shift);
68 }
69 
70 static __always_inline
71 unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
72 			       cycle_t *cycles, u8 *flags)
73 {
74 	unsigned version;
75 	cycle_t ret, offset;
76 	u8 ret_flags;
77 
78 	version = src->version;
79 	/* Note: emulated platforms which do not advertise SSE2 support
80 	 * result in kvmclock not using the necessary RDTSC barriers.
81 	 * Without barriers, it is possible that RDTSC instruction reads from
82 	 * the time stamp counter outside rdtsc_barrier protected section
83 	 * below, resulting in violation of monotonicity.
84 	 */
85 	rdtsc_barrier();
86 	offset = pvclock_get_nsec_offset(src);
87 	ret = src->system_time + offset;
88 	ret_flags = src->flags;
89 	rdtsc_barrier();
90 
91 	*cycles = ret;
92 	*flags = ret_flags;
93 	return version;
94 }
95 
96 struct pvclock_vsyscall_time_info {
97 	struct pvclock_vcpu_time_info pvti;
98 } __attribute__((__aligned__(SMP_CACHE_BYTES)));
99 
100 #define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
101 #define PVCLOCK_VSYSCALL_NR_PAGES (((NR_CPUS-1)/(PAGE_SIZE/PVTI_SIZE))+1)
102 
103 int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
104 				 int size);
105 struct pvclock_vcpu_time_info *pvclock_get_vsyscall_time_info(int cpu);
106 
107 #endif /* _ASM_X86_PVCLOCK_H */
108