1 /* KVM paravirtual clock driver. A clocksource implementation
2 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
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.
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.
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
19 #include <linux/clocksource.h>
20 #include <linux/kvm_para.h>
21 #include <asm/pvclock.h>
24 #include <linux/percpu.h>
25 #include <linux/hardirq.h>
26 #include <linux/memblock.h>
27 #include <linux/sched.h>
28 #include <linux/sched/clock.h>
30 #include <asm/x86_init.h>
31 #include <asm/reboot.h>
32 #include <asm/kvmclock.h>
34 static int kvmclock __ro_after_init
= 1;
35 static int msr_kvm_system_time
= MSR_KVM_SYSTEM_TIME
;
36 static int msr_kvm_wall_clock
= MSR_KVM_WALL_CLOCK
;
37 static u64 kvm_sched_clock_offset
;
39 static int parse_no_kvmclock(char *arg
)
44 early_param("no-kvmclock", parse_no_kvmclock
);
46 /* The hypervisor will put information about time periodically here */
47 static struct pvclock_vsyscall_time_info
*hv_clock
;
48 static struct pvclock_wall_clock wall_clock
;
50 struct pvclock_vsyscall_time_info
*pvclock_pvti_cpu0_va(void)
54 EXPORT_SYMBOL_GPL(pvclock_pvti_cpu0_va
);
57 * The wallclock is the time of day when we booted. Since then, some time may
58 * have elapsed since the hypervisor wrote the data. So we try to account for
59 * that with system time
61 static void kvm_get_wallclock(struct timespec
*now
)
63 struct pvclock_vcpu_time_info
*vcpu_time
;
67 low
= (int)__pa_symbol(&wall_clock
);
68 high
= ((u64
)__pa_symbol(&wall_clock
) >> 32);
70 native_write_msr(msr_kvm_wall_clock
, low
, high
);
74 vcpu_time
= &hv_clock
[cpu
].pvti
;
75 pvclock_read_wallclock(&wall_clock
, vcpu_time
, now
);
80 static int kvm_set_wallclock(const struct timespec
*now
)
85 static u64
kvm_clock_read(void)
87 struct pvclock_vcpu_time_info
*src
;
91 preempt_disable_notrace();
92 cpu
= smp_processor_id();
93 src
= &hv_clock
[cpu
].pvti
;
94 ret
= pvclock_clocksource_read(src
);
95 preempt_enable_notrace();
99 static u64
kvm_clock_get_cycles(struct clocksource
*cs
)
101 return kvm_clock_read();
104 static u64
kvm_sched_clock_read(void)
106 return kvm_clock_read() - kvm_sched_clock_offset
;
109 static inline void kvm_sched_clock_init(bool stable
)
112 pv_time_ops
.sched_clock
= kvm_clock_read
;
113 clear_sched_clock_stable();
117 kvm_sched_clock_offset
= kvm_clock_read();
118 pv_time_ops
.sched_clock
= kvm_sched_clock_read
;
120 printk(KERN_INFO
"kvm-clock: using sched offset of %llu cycles\n",
121 kvm_sched_clock_offset
);
123 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset
) >
124 sizeof(((struct pvclock_vcpu_time_info
*)NULL
)->system_time
));
128 * If we don't do that, there is the possibility that the guest
129 * will calibrate under heavy load - thus, getting a lower lpj -
130 * and execute the delays themselves without load. This is wrong,
131 * because no delay loop can finish beforehand.
132 * Any heuristics is subject to fail, because ultimately, a large
133 * poll of guests can be running and trouble each other. So we preset
136 static unsigned long kvm_get_tsc_khz(void)
138 struct pvclock_vcpu_time_info
*src
;
140 unsigned long tsc_khz
;
143 src
= &hv_clock
[cpu
].pvti
;
144 tsc_khz
= pvclock_tsc_khz(src
);
149 static void kvm_get_preset_lpj(void)
154 khz
= kvm_get_tsc_khz();
156 lpj
= ((u64
)khz
* 1000);
161 bool kvm_check_and_clear_guest_paused(void)
164 struct pvclock_vcpu_time_info
*src
;
165 int cpu
= smp_processor_id();
170 src
= &hv_clock
[cpu
].pvti
;
171 if ((src
->flags
& PVCLOCK_GUEST_STOPPED
) != 0) {
172 src
->flags
&= ~PVCLOCK_GUEST_STOPPED
;
173 pvclock_touch_watchdogs();
180 struct clocksource kvm_clock
= {
182 .read
= kvm_clock_get_cycles
,
184 .mask
= CLOCKSOURCE_MASK(64),
185 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
,
187 EXPORT_SYMBOL_GPL(kvm_clock
);
189 int kvm_register_clock(char *txt
)
191 int cpu
= smp_processor_id();
193 struct pvclock_vcpu_time_info
*src
;
198 src
= &hv_clock
[cpu
].pvti
;
199 low
= (int)slow_virt_to_phys(src
) | 1;
200 high
= ((u64
)slow_virt_to_phys(src
) >> 32);
201 ret
= native_write_msr_safe(msr_kvm_system_time
, low
, high
);
202 printk(KERN_INFO
"kvm-clock: cpu %d, msr %x:%x, %s\n",
203 cpu
, high
, low
, txt
);
208 static void kvm_save_sched_clock_state(void)
212 static void kvm_restore_sched_clock_state(void)
214 kvm_register_clock("primary cpu clock, resume");
217 #ifdef CONFIG_X86_LOCAL_APIC
218 static void kvm_setup_secondary_clock(void)
221 * Now that the first cpu already had this clocksource initialized,
224 WARN_ON(kvm_register_clock("secondary cpu clock"));
229 * After the clock is registered, the host will keep writing to the
230 * registered memory location. If the guest happens to shutdown, this memory
231 * won't be valid. In cases like kexec, in which you install a new kernel, this
232 * means a random memory location will be kept being written. So before any
233 * kind of shutdown from our side, we unregister the clock by writing anything
234 * that does not have the 'enable' bit set in the msr
236 #ifdef CONFIG_KEXEC_CORE
237 static void kvm_crash_shutdown(struct pt_regs
*regs
)
239 native_write_msr(msr_kvm_system_time
, 0, 0);
240 kvm_disable_steal_time();
241 native_machine_crash_shutdown(regs
);
245 static void kvm_shutdown(void)
247 native_write_msr(msr_kvm_system_time
, 0, 0);
248 kvm_disable_steal_time();
249 native_machine_shutdown();
252 void __init
kvmclock_init(void)
254 struct pvclock_vcpu_time_info
*vcpu_time
;
259 size
= PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info
)*NR_CPUS
);
261 if (!kvm_para_available())
264 if (kvmclock
&& kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2
)) {
265 msr_kvm_system_time
= MSR_KVM_SYSTEM_TIME_NEW
;
266 msr_kvm_wall_clock
= MSR_KVM_WALL_CLOCK_NEW
;
267 } else if (!(kvmclock
&& kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE
)))
270 printk(KERN_INFO
"kvm-clock: Using msrs %x and %x",
271 msr_kvm_system_time
, msr_kvm_wall_clock
);
273 mem
= memblock_alloc(size
, PAGE_SIZE
);
276 hv_clock
= __va(mem
);
277 memset(hv_clock
, 0, size
);
279 if (kvm_register_clock("primary cpu clock")) {
281 memblock_free(mem
, size
);
285 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT
))
286 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
);
289 vcpu_time
= &hv_clock
[cpu
].pvti
;
290 flags
= pvclock_read_flags(vcpu_time
);
292 kvm_sched_clock_init(flags
& PVCLOCK_TSC_STABLE_BIT
);
295 x86_platform
.calibrate_tsc
= kvm_get_tsc_khz
;
296 x86_platform
.calibrate_cpu
= kvm_get_tsc_khz
;
297 x86_platform
.get_wallclock
= kvm_get_wallclock
;
298 x86_platform
.set_wallclock
= kvm_set_wallclock
;
299 #ifdef CONFIG_X86_LOCAL_APIC
300 x86_cpuinit
.early_percpu_clock_init
=
301 kvm_setup_secondary_clock
;
303 x86_platform
.save_sched_clock_state
= kvm_save_sched_clock_state
;
304 x86_platform
.restore_sched_clock_state
= kvm_restore_sched_clock_state
;
305 machine_ops
.shutdown
= kvm_shutdown
;
306 #ifdef CONFIG_KEXEC_CORE
307 machine_ops
.crash_shutdown
= kvm_crash_shutdown
;
309 kvm_get_preset_lpj();
310 clocksource_register_hz(&kvm_clock
, NSEC_PER_SEC
);
311 pv_info
.name
= "KVM";
314 int __init
kvm_setup_vsyscall_timeinfo(void)
319 struct pvclock_vcpu_time_info
*vcpu_time
;
325 size
= PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info
)*NR_CPUS
);
329 vcpu_time
= &hv_clock
[cpu
].pvti
;
330 flags
= pvclock_read_flags(vcpu_time
);
332 if (!(flags
& PVCLOCK_TSC_STABLE_BIT
)) {
339 kvm_clock
.archdata
.vclock_mode
= VCLOCK_PVCLOCK
;