Commit | Line | Data |
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790c73f6 GOC |
1 | /* KVM paravirtual clock driver. A clocksource implementation |
2 | Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc. | |
3 | ||
4 | This program is free software; you can redistribute it and/or modify | |
5 | it under the terms of the GNU General Public License as published by | |
6 | the Free Software Foundation; either version 2 of the License, or | |
7 | (at your option) any later version. | |
8 | ||
9 | This program is distributed in the hope that it will be useful, | |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
12 | GNU General Public License for more details. | |
13 | ||
14 | You should have received a copy of the GNU General Public License | |
15 | along with this program; if not, write to the Free Software | |
16 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA | |
17 | */ | |
18 | ||
19 | #include <linux/clocksource.h> | |
20 | #include <linux/kvm_para.h> | |
21 | #include <asm/arch_hooks.h> | |
22 | #include <asm/msr.h> | |
23 | #include <asm/apic.h> | |
24 | #include <linux/percpu.h> | |
1e977aa1 | 25 | #include <asm/reboot.h> |
790c73f6 GOC |
26 | |
27 | #define KVM_SCALE 22 | |
28 | ||
29 | static int kvmclock = 1; | |
30 | ||
31 | static int parse_no_kvmclock(char *arg) | |
32 | { | |
33 | kvmclock = 0; | |
34 | return 0; | |
35 | } | |
36 | early_param("no-kvmclock", parse_no_kvmclock); | |
37 | ||
38 | /* The hypervisor will put information about time periodically here */ | |
39 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct kvm_vcpu_time_info, hv_clock); | |
40 | #define get_clock(cpu, field) per_cpu(hv_clock, cpu).field | |
41 | ||
42 | static inline u64 kvm_get_delta(u64 last_tsc) | |
43 | { | |
44 | int cpu = smp_processor_id(); | |
45 | u64 delta = native_read_tsc() - last_tsc; | |
46 | return (delta * get_clock(cpu, tsc_to_system_mul)) >> KVM_SCALE; | |
47 | } | |
48 | ||
49 | static struct kvm_wall_clock wall_clock; | |
50 | static cycle_t kvm_clock_read(void); | |
51 | /* | |
52 | * The wallclock is the time of day when we booted. Since then, some time may | |
53 | * have elapsed since the hypervisor wrote the data. So we try to account for | |
54 | * that with system time | |
55 | */ | |
2ddfd20e | 56 | static unsigned long kvm_get_wallclock(void) |
790c73f6 GOC |
57 | { |
58 | u32 wc_sec, wc_nsec; | |
59 | u64 delta; | |
60 | struct timespec ts; | |
61 | int version, nsec; | |
62 | int low, high; | |
63 | ||
64 | low = (int)__pa(&wall_clock); | |
65 | high = ((u64)__pa(&wall_clock) >> 32); | |
66 | ||
67 | delta = kvm_clock_read(); | |
68 | ||
69 | native_write_msr(MSR_KVM_WALL_CLOCK, low, high); | |
70 | do { | |
71 | version = wall_clock.wc_version; | |
72 | rmb(); | |
73 | wc_sec = wall_clock.wc_sec; | |
74 | wc_nsec = wall_clock.wc_nsec; | |
75 | rmb(); | |
76 | } while ((wall_clock.wc_version != version) || (version & 1)); | |
77 | ||
78 | delta = kvm_clock_read() - delta; | |
79 | delta += wc_nsec; | |
80 | nsec = do_div(delta, NSEC_PER_SEC); | |
81 | set_normalized_timespec(&ts, wc_sec + delta, nsec); | |
82 | /* | |
83 | * Of all mechanisms of time adjustment I've tested, this one | |
84 | * was the champion! | |
85 | */ | |
86 | return ts.tv_sec + 1; | |
87 | } | |
88 | ||
2ddfd20e | 89 | static int kvm_set_wallclock(unsigned long now) |
790c73f6 GOC |
90 | { |
91 | return 0; | |
92 | } | |
93 | ||
94 | /* | |
95 | * This is our read_clock function. The host puts an tsc timestamp each time | |
96 | * it updates a new time. Without the tsc adjustment, we can have a situation | |
97 | * in which a vcpu starts to run earlier (smaller system_time), but probes | |
98 | * time later (compared to another vcpu), leading to backwards time | |
99 | */ | |
100 | static cycle_t kvm_clock_read(void) | |
101 | { | |
102 | u64 last_tsc, now; | |
103 | int cpu; | |
104 | ||
105 | preempt_disable(); | |
106 | cpu = smp_processor_id(); | |
107 | ||
108 | last_tsc = get_clock(cpu, tsc_timestamp); | |
109 | now = get_clock(cpu, system_time); | |
110 | ||
111 | now += kvm_get_delta(last_tsc); | |
112 | preempt_enable(); | |
113 | ||
114 | return now; | |
115 | } | |
116 | static struct clocksource kvm_clock = { | |
117 | .name = "kvm-clock", | |
118 | .read = kvm_clock_read, | |
119 | .rating = 400, | |
120 | .mask = CLOCKSOURCE_MASK(64), | |
121 | .mult = 1 << KVM_SCALE, | |
122 | .shift = KVM_SCALE, | |
123 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, | |
124 | }; | |
125 | ||
126 | static int kvm_register_clock(void) | |
127 | { | |
128 | int cpu = smp_processor_id(); | |
129 | int low, high; | |
130 | low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1; | |
131 | high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32); | |
132 | ||
133 | return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high); | |
134 | } | |
135 | ||
b8ba5f10 | 136 | #ifdef CONFIG_X86_LOCAL_APIC |
790c73f6 GOC |
137 | static void kvm_setup_secondary_clock(void) |
138 | { | |
139 | /* | |
140 | * Now that the first cpu already had this clocksource initialized, | |
141 | * we shouldn't fail. | |
142 | */ | |
143 | WARN_ON(kvm_register_clock()); | |
144 | /* ok, done with our trickery, call native */ | |
145 | setup_secondary_APIC_clock(); | |
146 | } | |
b8ba5f10 | 147 | #endif |
790c73f6 | 148 | |
1e977aa1 GC |
149 | /* |
150 | * After the clock is registered, the host will keep writing to the | |
151 | * registered memory location. If the guest happens to shutdown, this memory | |
152 | * won't be valid. In cases like kexec, in which you install a new kernel, this | |
153 | * means a random memory location will be kept being written. So before any | |
154 | * kind of shutdown from our side, we unregister the clock by writting anything | |
155 | * that does not have the 'enable' bit set in the msr | |
156 | */ | |
157 | #ifdef CONFIG_KEXEC | |
158 | static void kvm_crash_shutdown(struct pt_regs *regs) | |
159 | { | |
160 | native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); | |
161 | native_machine_crash_shutdown(regs); | |
162 | } | |
163 | #endif | |
164 | ||
165 | static void kvm_shutdown(void) | |
166 | { | |
167 | native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); | |
168 | native_machine_shutdown(); | |
169 | } | |
170 | ||
790c73f6 GOC |
171 | void __init kvmclock_init(void) |
172 | { | |
173 | if (!kvm_para_available()) | |
174 | return; | |
175 | ||
176 | if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { | |
177 | if (kvm_register_clock()) | |
178 | return; | |
179 | pv_time_ops.get_wallclock = kvm_get_wallclock; | |
180 | pv_time_ops.set_wallclock = kvm_set_wallclock; | |
181 | pv_time_ops.sched_clock = kvm_clock_read; | |
b8ba5f10 | 182 | #ifdef CONFIG_X86_LOCAL_APIC |
790c73f6 | 183 | pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock; |
b8ba5f10 | 184 | #endif |
1e977aa1 GC |
185 | machine_ops.shutdown = kvm_shutdown; |
186 | #ifdef CONFIG_KEXEC | |
187 | machine_ops.crash_shutdown = kvm_crash_shutdown; | |
188 | #endif | |
790c73f6 GOC |
189 | clocksource_register(&kvm_clock); |
190 | } | |
191 | } |