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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/pvclock.h>
22 #include <asm/msr.h>
23 #include <asm/apic.h>
24 #include <linux/percpu.h>
25 #include <linux/hardirq.h>
26 #include <linux/memblock.h>
27 #include <linux/sched.h>
28
29 #include <asm/x86_init.h>
30 #include <asm/reboot.h>
31
32 static int kvmclock = 1;
33 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
34 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
35 static cycle_t kvm_sched_clock_offset;
36
37 static int parse_no_kvmclock(char *arg)
38 {
39 kvmclock = 0;
40 return 0;
41 }
42 early_param("no-kvmclock", parse_no_kvmclock);
43
44 /* The hypervisor will put information about time periodically here */
45 static struct pvclock_vsyscall_time_info *hv_clock;
46 static struct pvclock_wall_clock wall_clock;
47
48 /*
49 * The wallclock is the time of day when we booted. Since then, some time may
50 * have elapsed since the hypervisor wrote the data. So we try to account for
51 * that with system time
52 */
53 static void kvm_get_wallclock(struct timespec *now)
54 {
55 struct pvclock_vcpu_time_info *vcpu_time;
56 int low, high;
57 int cpu;
58
59 low = (int)__pa_symbol(&wall_clock);
60 high = ((u64)__pa_symbol(&wall_clock) >> 32);
61
62 native_write_msr(msr_kvm_wall_clock, low, high);
63
64 cpu = get_cpu();
65
66 vcpu_time = &hv_clock[cpu].pvti;
67 pvclock_read_wallclock(&wall_clock, vcpu_time, now);
68
69 put_cpu();
70 }
71
72 static int kvm_set_wallclock(const struct timespec *now)
73 {
74 return -1;
75 }
76
77 static cycle_t kvm_clock_read(void)
78 {
79 struct pvclock_vcpu_time_info *src;
80 cycle_t ret;
81 int cpu;
82
83 preempt_disable_notrace();
84 cpu = smp_processor_id();
85 src = &hv_clock[cpu].pvti;
86 ret = pvclock_clocksource_read(src);
87 preempt_enable_notrace();
88 return ret;
89 }
90
91 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
92 {
93 return kvm_clock_read();
94 }
95
96 static cycle_t kvm_sched_clock_read(void)
97 {
98 return kvm_clock_read() - kvm_sched_clock_offset;
99 }
100
101 static inline void kvm_sched_clock_init(bool stable)
102 {
103 if (!stable) {
104 pv_time_ops.sched_clock = kvm_clock_read;
105 return;
106 }
107
108 kvm_sched_clock_offset = kvm_clock_read();
109 pv_time_ops.sched_clock = kvm_sched_clock_read;
110 set_sched_clock_stable();
111
112 printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
113 kvm_sched_clock_offset);
114
115 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
116 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
117 }
118
119 /*
120 * If we don't do that, there is the possibility that the guest
121 * will calibrate under heavy load - thus, getting a lower lpj -
122 * and execute the delays themselves without load. This is wrong,
123 * because no delay loop can finish beforehand.
124 * Any heuristics is subject to fail, because ultimately, a large
125 * poll of guests can be running and trouble each other. So we preset
126 * lpj here
127 */
128 static unsigned long kvm_get_tsc_khz(void)
129 {
130 struct pvclock_vcpu_time_info *src;
131 int cpu;
132 unsigned long tsc_khz;
133
134 cpu = get_cpu();
135 src = &hv_clock[cpu].pvti;
136 tsc_khz = pvclock_tsc_khz(src);
137 put_cpu();
138 return tsc_khz;
139 }
140
141 static void kvm_get_preset_lpj(void)
142 {
143 unsigned long khz;
144 u64 lpj;
145
146 khz = kvm_get_tsc_khz();
147
148 lpj = ((u64)khz * 1000);
149 do_div(lpj, HZ);
150 preset_lpj = lpj;
151 }
152
153 bool kvm_check_and_clear_guest_paused(void)
154 {
155 bool ret = false;
156 struct pvclock_vcpu_time_info *src;
157 int cpu = smp_processor_id();
158
159 if (!hv_clock)
160 return ret;
161
162 src = &hv_clock[cpu].pvti;
163 if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
164 src->flags &= ~PVCLOCK_GUEST_STOPPED;
165 pvclock_touch_watchdogs();
166 ret = true;
167 }
168
169 return ret;
170 }
171
172 static struct clocksource kvm_clock = {
173 .name = "kvm-clock",
174 .read = kvm_clock_get_cycles,
175 .rating = 400,
176 .mask = CLOCKSOURCE_MASK(64),
177 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
178 };
179
180 int kvm_register_clock(char *txt)
181 {
182 int cpu = smp_processor_id();
183 int low, high, ret;
184 struct pvclock_vcpu_time_info *src;
185
186 if (!hv_clock)
187 return 0;
188
189 src = &hv_clock[cpu].pvti;
190 low = (int)slow_virt_to_phys(src) | 1;
191 high = ((u64)slow_virt_to_phys(src) >> 32);
192 ret = native_write_msr_safe(msr_kvm_system_time, low, high);
193 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
194 cpu, high, low, txt);
195
196 return ret;
197 }
198
199 static void kvm_save_sched_clock_state(void)
200 {
201 }
202
203 static void kvm_restore_sched_clock_state(void)
204 {
205 kvm_register_clock("primary cpu clock, resume");
206 }
207
208 #ifdef CONFIG_X86_LOCAL_APIC
209 static void kvm_setup_secondary_clock(void)
210 {
211 /*
212 * Now that the first cpu already had this clocksource initialized,
213 * we shouldn't fail.
214 */
215 WARN_ON(kvm_register_clock("secondary cpu clock"));
216 }
217 #endif
218
219 /*
220 * After the clock is registered, the host will keep writing to the
221 * registered memory location. If the guest happens to shutdown, this memory
222 * won't be valid. In cases like kexec, in which you install a new kernel, this
223 * means a random memory location will be kept being written. So before any
224 * kind of shutdown from our side, we unregister the clock by writting anything
225 * that does not have the 'enable' bit set in the msr
226 */
227 #ifdef CONFIG_KEXEC_CORE
228 static void kvm_crash_shutdown(struct pt_regs *regs)
229 {
230 native_write_msr(msr_kvm_system_time, 0, 0);
231 kvm_disable_steal_time();
232 native_machine_crash_shutdown(regs);
233 }
234 #endif
235
236 static void kvm_shutdown(void)
237 {
238 native_write_msr(msr_kvm_system_time, 0, 0);
239 kvm_disable_steal_time();
240 native_machine_shutdown();
241 }
242
243 void __init kvmclock_init(void)
244 {
245 struct pvclock_vcpu_time_info *vcpu_time;
246 unsigned long mem;
247 int size, cpu;
248 u8 flags;
249
250 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
251
252 if (!kvm_para_available())
253 return;
254
255 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
256 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
257 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
258 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
259 return;
260
261 printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
262 msr_kvm_system_time, msr_kvm_wall_clock);
263
264 mem = memblock_alloc(size, PAGE_SIZE);
265 if (!mem)
266 return;
267 hv_clock = __va(mem);
268 memset(hv_clock, 0, size);
269
270 if (kvm_register_clock("primary cpu clock")) {
271 hv_clock = NULL;
272 memblock_free(mem, size);
273 return;
274 }
275
276 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
277 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
278
279 cpu = get_cpu();
280 vcpu_time = &hv_clock[cpu].pvti;
281 flags = pvclock_read_flags(vcpu_time);
282
283 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
284 put_cpu();
285
286 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
287 x86_platform.get_wallclock = kvm_get_wallclock;
288 x86_platform.set_wallclock = kvm_set_wallclock;
289 #ifdef CONFIG_X86_LOCAL_APIC
290 x86_cpuinit.early_percpu_clock_init =
291 kvm_setup_secondary_clock;
292 #endif
293 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
294 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
295 machine_ops.shutdown = kvm_shutdown;
296 #ifdef CONFIG_KEXEC_CORE
297 machine_ops.crash_shutdown = kvm_crash_shutdown;
298 #endif
299 kvm_get_preset_lpj();
300 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
301 pv_info.name = "KVM";
302 }
303
304 int __init kvm_setup_vsyscall_timeinfo(void)
305 {
306 #ifdef CONFIG_X86_64
307 int cpu;
308 int ret;
309 u8 flags;
310 struct pvclock_vcpu_time_info *vcpu_time;
311 unsigned int size;
312
313 if (!hv_clock)
314 return 0;
315
316 size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
317
318 cpu = get_cpu();
319
320 vcpu_time = &hv_clock[cpu].pvti;
321 flags = pvclock_read_flags(vcpu_time);
322
323 if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
324 put_cpu();
325 return 1;
326 }
327
328 if ((ret = pvclock_init_vsyscall(hv_clock, size))) {
329 put_cpu();
330 return ret;
331 }
332
333 put_cpu();
334
335 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
336 #endif
337 return 0;
338 }