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