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-rw-r--r--arch/x86/Kconfig4
-rw-r--r--arch/x86/kernel/Makefile1
-rw-r--r--arch/x86/kernel/pvclock.c141
-rw-r--r--include/asm-x86/pvclock-abi.h42
-rw-r--r--include/asm-x86/pvclock.h13
5 files changed, 201 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 52e18e6d2ba0..f94bca6ff47f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -410,6 +410,10 @@ config PARAVIRT
410 over full virtualization. However, when run without a hypervisor 410 over full virtualization. However, when run without a hypervisor
411 the kernel is theoretically slower and slightly larger. 411 the kernel is theoretically slower and slightly larger.
412 412
413config PARAVIRT_CLOCK
414 bool
415 default n
416
413endif 417endif
414 418
415config MEMTEST_BOOTPARAM 419config MEMTEST_BOOTPARAM
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 5e618c3b4720..77807d4769c9 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_VMI) += vmi_32.o vmiclock_32.o
82obj-$(CONFIG_KVM_GUEST) += kvm.o 82obj-$(CONFIG_KVM_GUEST) += kvm.o
83obj-$(CONFIG_KVM_CLOCK) += kvmclock.o 83obj-$(CONFIG_KVM_CLOCK) += kvmclock.o
84obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o 84obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o
85obj-$(CONFIG_PARAVIRT_CLOCK) += pvclock.o
85 86
86obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o 87obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o
87 88
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
new file mode 100644
index 000000000000..05fbe9a0325a
--- /dev/null
+++ b/arch/x86/kernel/pvclock.c
@@ -0,0 +1,141 @@
1/* paravirtual clock -- common code used by kvm/xen
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; either version 2 of the License, or
6 (at your option) any later version.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
16*/
17
18#include <linux/kernel.h>
19#include <linux/percpu.h>
20#include <asm/pvclock.h>
21
22/*
23 * These are perodically updated
24 * xen: magic shared_info page
25 * kvm: gpa registered via msr
26 * and then copied here.
27 */
28struct pvclock_shadow_time {
29 u64 tsc_timestamp; /* TSC at last update of time vals. */
30 u64 system_timestamp; /* Time, in nanosecs, since boot. */
31 u32 tsc_to_nsec_mul;
32 int tsc_shift;
33 u32 version;
34};
35
36/*
37 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
38 * yielding a 64-bit result.
39 */
40static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
41{
42 u64 product;
43#ifdef __i386__
44 u32 tmp1, tmp2;
45#endif
46
47 if (shift < 0)
48 delta >>= -shift;
49 else
50 delta <<= shift;
51
52#ifdef __i386__
53 __asm__ (
54 "mul %5 ; "
55 "mov %4,%%eax ; "
56 "mov %%edx,%4 ; "
57 "mul %5 ; "
58 "xor %5,%5 ; "
59 "add %4,%%eax ; "
60 "adc %5,%%edx ; "
61 : "=A" (product), "=r" (tmp1), "=r" (tmp2)
62 : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
63#elif __x86_64__
64 __asm__ (
65 "mul %%rdx ; shrd $32,%%rdx,%%rax"
66 : "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
67#else
68#error implement me!
69#endif
70
71 return product;
72}
73
74static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow)
75{
76 u64 delta = native_read_tsc() - shadow->tsc_timestamp;
77 return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
78}
79
80/*
81 * Reads a consistent set of time-base values from hypervisor,
82 * into a shadow data area.
83 */
84static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst,
85 struct pvclock_vcpu_time_info *src)
86{
87 do {
88 dst->version = src->version;
89 rmb(); /* fetch version before data */
90 dst->tsc_timestamp = src->tsc_timestamp;
91 dst->system_timestamp = src->system_time;
92 dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
93 dst->tsc_shift = src->tsc_shift;
94 rmb(); /* test version after fetching data */
95 } while ((src->version & 1) || (dst->version != src->version));
96
97 return dst->version;
98}
99
100cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
101{
102 struct pvclock_shadow_time shadow;
103 unsigned version;
104 cycle_t ret, offset;
105
106 do {
107 version = pvclock_get_time_values(&shadow, src);
108 barrier();
109 offset = pvclock_get_nsec_offset(&shadow);
110 ret = shadow.system_timestamp + offset;
111 barrier();
112 } while (version != src->version);
113
114 return ret;
115}
116
117void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
118 struct pvclock_vcpu_time_info *vcpu_time,
119 struct timespec *ts)
120{
121 u32 version;
122 u64 delta;
123 struct timespec now;
124
125 /* get wallclock at system boot */
126 do {
127 version = wall_clock->version;
128 rmb(); /* fetch version before time */
129 now.tv_sec = wall_clock->sec;
130 now.tv_nsec = wall_clock->nsec;
131 rmb(); /* fetch time before checking version */
132 } while ((wall_clock->version & 1) || (version != wall_clock->version));
133
134 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
135 delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
136
137 now.tv_nsec = do_div(delta, NSEC_PER_SEC);
138 now.tv_sec = delta;
139
140 set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
141}
diff --git a/include/asm-x86/pvclock-abi.h b/include/asm-x86/pvclock-abi.h
new file mode 100644
index 000000000000..6857f840b243
--- /dev/null
+++ b/include/asm-x86/pvclock-abi.h
@@ -0,0 +1,42 @@
1#ifndef _ASM_X86_PVCLOCK_ABI_H_
2#define _ASM_X86_PVCLOCK_ABI_H_
3#ifndef __ASSEMBLY__
4
5/*
6 * These structs MUST NOT be changed.
7 * They are the ABI between hypervisor and guest OS.
8 * Both Xen and KVM are using this.
9 *
10 * pvclock_vcpu_time_info holds the system time and the tsc timestamp
11 * of the last update. So the guest can use the tsc delta to get a
12 * more precise system time. There is one per virtual cpu.
13 *
14 * pvclock_wall_clock references the point in time when the system
15 * time was zero (usually boot time), thus the guest calculates the
16 * current wall clock by adding the system time.
17 *
18 * Protocol for the "version" fields is: hypervisor raises it (making
19 * it uneven) before it starts updating the fields and raises it again
20 * (making it even) when it is done. Thus the guest can make sure the
21 * time values it got are consistent by checking the version before
22 * and after reading them.
23 */
24
25struct pvclock_vcpu_time_info {
26 u32 version;
27 u32 pad0;
28 u64 tsc_timestamp;
29 u64 system_time;
30 u32 tsc_to_system_mul;
31 s8 tsc_shift;
32 u8 pad[3];
33} __attribute__((__packed__)); /* 32 bytes */
34
35struct pvclock_wall_clock {
36 u32 version;
37 u32 sec;
38 u32 nsec;
39} __attribute__((__packed__));
40
41#endif /* __ASSEMBLY__ */
42#endif /* _ASM_X86_PVCLOCK_ABI_H_ */
diff --git a/include/asm-x86/pvclock.h b/include/asm-x86/pvclock.h
new file mode 100644
index 000000000000..85b1bba8e0a3
--- /dev/null
+++ b/include/asm-x86/pvclock.h
@@ -0,0 +1,13 @@
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 */
8cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
9void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
10 struct pvclock_vcpu_time_info *vcpu,
11 struct timespec *ts);
12
13#endif /* _ASM_X86_PVCLOCK_H_ */
generated by cgit v1.2.2 (git 2.25.0) at 2025-12-26 07:36:20 -0500