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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
26#include <asm/x86_init.h>
27#include <asm/reboot.h>
28
29static int kvmclock = 1;
30static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
31static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
32
33static int parse_no_kvmclock(char *arg)
34{
35 kvmclock = 0;
36 return 0;
37}
38early_param("no-kvmclock", parse_no_kvmclock);
39
40/* The hypervisor will put information about time periodically here */
41static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
42static struct pvclock_wall_clock wall_clock;
43
44/*
45 * The wallclock is the time of day when we booted. Since then, some time may
46 * have elapsed since the hypervisor wrote the data. So we try to account for
47 * that with system time
48 */
49static unsigned long kvm_get_wallclock(void)
50{
51 struct pvclock_vcpu_time_info *vcpu_time;
52 struct timespec ts;
53 int low, high;
54
55 low = (int)__pa_symbol(&wall_clock);
56 high = ((u64)__pa_symbol(&wall_clock) >> 32);
57
58 native_write_msr(msr_kvm_wall_clock, low, high);
59
60 vcpu_time = &get_cpu_var(hv_clock);
61 pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
62 put_cpu_var(hv_clock);
63
64 return ts.tv_sec;
65}
66
67static int kvm_set_wallclock(unsigned long now)
68{
69 return -1;
70}
71
72static cycle_t kvm_clock_read(void)
73{
74 struct pvclock_vcpu_time_info *src;
75 cycle_t ret;
76
77 src = &get_cpu_var(hv_clock);
78 ret = pvclock_clocksource_read(src);
79 put_cpu_var(hv_clock);
80 return ret;
81}
82
83static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
84{
85 return kvm_clock_read();
86}
87
88/*
89 * If we don't do that, there is the possibility that the guest
90 * will calibrate under heavy load - thus, getting a lower lpj -
91 * and execute the delays themselves without load. This is wrong,
92 * because no delay loop can finish beforehand.
93 * Any heuristics is subject to fail, because ultimately, a large
94 * poll of guests can be running and trouble each other. So we preset
95 * lpj here
96 */
97static unsigned long kvm_get_tsc_khz(void)
98{
99 struct pvclock_vcpu_time_info *src;
100 src = &per_cpu(hv_clock, 0);
101 return pvclock_tsc_khz(src);
102}
103
104static void kvm_get_preset_lpj(void)
105{
106 unsigned long khz;
107 u64 lpj;
108
109 khz = kvm_get_tsc_khz();
110
111 lpj = ((u64)khz * 1000);
112 do_div(lpj, HZ);
113 preset_lpj = lpj;
114}
115
116static struct clocksource kvm_clock = {
117 .name = "kvm-clock",
118 .read = kvm_clock_get_cycles,
119 .rating = 400,
120 .mask = CLOCKSOURCE_MASK(64),
121 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
122};
123
124int kvm_register_clock(char *txt)
125{
126 int cpu = smp_processor_id();
127 int low, high, ret;
128
129 low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
130 high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
131 ret = native_write_msr_safe(msr_kvm_system_time, low, high);
132 printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
133 cpu, high, low, txt);
134
135 return ret;
136}
137
138#ifdef CONFIG_X86_LOCAL_APIC
139static void __cpuinit kvm_setup_secondary_clock(void)
140{
141 /*
142 * Now that the first cpu already had this clocksource initialized,
143 * we shouldn't fail.
144 */
145 WARN_ON(kvm_register_clock("secondary cpu clock"));
146 /* ok, done with our trickery, call native */
147 setup_secondary_APIC_clock();
148}
149#endif
150
151/*
152 * After the clock is registered, the host will keep writing to the
153 * registered memory location. If the guest happens to shutdown, this memory
154 * won't be valid. In cases like kexec, in which you install a new kernel, this
155 * means a random memory location will be kept being written. So before any
156 * kind of shutdown from our side, we unregister the clock by writting anything
157 * that does not have the 'enable' bit set in the msr
158 */
159#ifdef CONFIG_KEXEC
160static void kvm_crash_shutdown(struct pt_regs *regs)
161{
162 native_write_msr(msr_kvm_system_time, 0, 0);
163 kvm_disable_steal_time();
164 native_machine_crash_shutdown(regs);
165}
166#endif
167
168static void kvm_shutdown(void)
169{
170 native_write_msr(msr_kvm_system_time, 0, 0);
171 kvm_disable_steal_time();
172 native_machine_shutdown();
173}
174
175void __init kvmclock_init(void)
176{
177 if (!kvm_para_available())
178 return;
179
180 if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
181 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
182 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
183 } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
184 return;
185
186 printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
187 msr_kvm_system_time, msr_kvm_wall_clock);
188
189 if (kvm_register_clock("boot clock"))
190 return;
191 pv_time_ops.sched_clock = kvm_clock_read;
192 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
193 x86_platform.get_wallclock = kvm_get_wallclock;
194 x86_platform.set_wallclock = kvm_set_wallclock;
195#ifdef CONFIG_X86_LOCAL_APIC
196 x86_cpuinit.setup_percpu_clockev =
197 kvm_setup_secondary_clock;
198#endif
199 machine_ops.shutdown = kvm_shutdown;
200#ifdef CONFIG_KEXEC
201 machine_ops.crash_shutdown = kvm_crash_shutdown;
202#endif
203 kvm_get_preset_lpj();
204 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
205 pv_info.paravirt_enabled = 1;
206 pv_info.name = "KVM";
207
208 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
209 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
210}
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* KVM paravirtual clock driver. A clocksource implementation
3 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
4*/
5
6#include <linux/clocksource.h>
7#include <linux/kvm_para.h>
8#include <asm/pvclock.h>
9#include <asm/msr.h>
10#include <asm/apic.h>
11#include <linux/percpu.h>
12#include <linux/hardirq.h>
13#include <linux/cpuhotplug.h>
14#include <linux/sched.h>
15#include <linux/sched/clock.h>
16#include <linux/mm.h>
17#include <linux/slab.h>
18#include <linux/set_memory.h>
19
20#include <asm/hypervisor.h>
21#include <asm/mem_encrypt.h>
22#include <asm/x86_init.h>
23#include <asm/reboot.h>
24#include <asm/kvmclock.h>
25
26static int kvmclock __initdata = 1;
27static int kvmclock_vsyscall __initdata = 1;
28static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME;
29static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK;
30static u64 kvm_sched_clock_offset __ro_after_init;
31
32static int __init parse_no_kvmclock(char *arg)
33{
34 kvmclock = 0;
35 return 0;
36}
37early_param("no-kvmclock", parse_no_kvmclock);
38
39static int __init parse_no_kvmclock_vsyscall(char *arg)
40{
41 kvmclock_vsyscall = 0;
42 return 0;
43}
44early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
45
46/* Aligned to page sizes to match whats mapped via vsyscalls to userspace */
47#define HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS)
48#define HVC_BOOT_ARRAY_SIZE \
49 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
50
51static struct pvclock_vsyscall_time_info
52 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
53static struct pvclock_wall_clock wall_clock __bss_decrypted;
54static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
55static struct pvclock_vsyscall_time_info *hvclock_mem;
56
57static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void)
58{
59 return &this_cpu_read(hv_clock_per_cpu)->pvti;
60}
61
62static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void)
63{
64 return this_cpu_read(hv_clock_per_cpu);
65}
66
67/*
68 * The wallclock is the time of day when we booted. Since then, some time may
69 * have elapsed since the hypervisor wrote the data. So we try to account for
70 * that with system time
71 */
72static void kvm_get_wallclock(struct timespec64 *now)
73{
74 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
75 preempt_disable();
76 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
77 preempt_enable();
78}
79
80static int kvm_set_wallclock(const struct timespec64 *now)
81{
82 return -ENODEV;
83}
84
85static u64 kvm_clock_read(void)
86{
87 u64 ret;
88
89 preempt_disable_notrace();
90 ret = pvclock_clocksource_read(this_cpu_pvti());
91 preempt_enable_notrace();
92 return ret;
93}
94
95static u64 kvm_clock_get_cycles(struct clocksource *cs)
96{
97 return kvm_clock_read();
98}
99
100static u64 kvm_sched_clock_read(void)
101{
102 return kvm_clock_read() - kvm_sched_clock_offset;
103}
104
105static inline void kvm_sched_clock_init(bool stable)
106{
107 if (!stable)
108 clear_sched_clock_stable();
109 kvm_sched_clock_offset = kvm_clock_read();
110 pv_ops.time.sched_clock = kvm_sched_clock_read;
111
112 pr_info("kvm-clock: using sched offset of %llu cycles",
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 */
128static unsigned long kvm_get_tsc_khz(void)
129{
130 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
131 return pvclock_tsc_khz(this_cpu_pvti());
132}
133
134static void __init kvm_get_preset_lpj(void)
135{
136 unsigned long khz;
137 u64 lpj;
138
139 khz = kvm_get_tsc_khz();
140
141 lpj = ((u64)khz * 1000);
142 do_div(lpj, HZ);
143 preset_lpj = lpj;
144}
145
146bool kvm_check_and_clear_guest_paused(void)
147{
148 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
149 bool ret = false;
150
151 if (!src)
152 return ret;
153
154 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
155 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
156 pvclock_touch_watchdogs();
157 ret = true;
158 }
159 return ret;
160}
161
162static int kvm_cs_enable(struct clocksource *cs)
163{
164 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
165 return 0;
166}
167
168struct clocksource kvm_clock = {
169 .name = "kvm-clock",
170 .read = kvm_clock_get_cycles,
171 .rating = 400,
172 .mask = CLOCKSOURCE_MASK(64),
173 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
174 .enable = kvm_cs_enable,
175};
176EXPORT_SYMBOL_GPL(kvm_clock);
177
178static void kvm_register_clock(char *txt)
179{
180 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
181 u64 pa;
182
183 if (!src)
184 return;
185
186 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
187 wrmsrl(msr_kvm_system_time, pa);
188 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
189}
190
191static void kvm_save_sched_clock_state(void)
192{
193}
194
195static void kvm_restore_sched_clock_state(void)
196{
197 kvm_register_clock("primary cpu clock, resume");
198}
199
200#ifdef CONFIG_X86_LOCAL_APIC
201static void kvm_setup_secondary_clock(void)
202{
203 kvm_register_clock("secondary cpu clock");
204}
205#endif
206
207/*
208 * After the clock is registered, the host will keep writing to the
209 * registered memory location. If the guest happens to shutdown, this memory
210 * won't be valid. In cases like kexec, in which you install a new kernel, this
211 * means a random memory location will be kept being written. So before any
212 * kind of shutdown from our side, we unregister the clock by writing anything
213 * that does not have the 'enable' bit set in the msr
214 */
215#ifdef CONFIG_KEXEC_CORE
216static void kvm_crash_shutdown(struct pt_regs *regs)
217{
218 native_write_msr(msr_kvm_system_time, 0, 0);
219 kvm_disable_steal_time();
220 native_machine_crash_shutdown(regs);
221}
222#endif
223
224static void kvm_shutdown(void)
225{
226 native_write_msr(msr_kvm_system_time, 0, 0);
227 kvm_disable_steal_time();
228 native_machine_shutdown();
229}
230
231static void __init kvmclock_init_mem(void)
232{
233 unsigned long ncpus;
234 unsigned int order;
235 struct page *p;
236 int r;
237
238 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
239 return;
240
241 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
242 order = get_order(ncpus * sizeof(*hvclock_mem));
243
244 p = alloc_pages(GFP_KERNEL, order);
245 if (!p) {
246 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
247 return;
248 }
249
250 hvclock_mem = page_address(p);
251
252 /*
253 * hvclock is shared between the guest and the hypervisor, must
254 * be mapped decrypted.
255 */
256 if (sev_active()) {
257 r = set_memory_decrypted((unsigned long) hvclock_mem,
258 1UL << order);
259 if (r) {
260 __free_pages(p, order);
261 hvclock_mem = NULL;
262 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
263 return;
264 }
265 }
266
267 memset(hvclock_mem, 0, PAGE_SIZE << order);
268}
269
270static int __init kvm_setup_vsyscall_timeinfo(void)
271{
272#ifdef CONFIG_X86_64
273 u8 flags;
274
275 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall)
276 return 0;
277
278 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
279 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
280 return 0;
281
282 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
283#endif
284
285 kvmclock_init_mem();
286
287 return 0;
288}
289early_initcall(kvm_setup_vsyscall_timeinfo);
290
291static int kvmclock_setup_percpu(unsigned int cpu)
292{
293 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
294
295 /*
296 * The per cpu area setup replicates CPU0 data to all cpu
297 * pointers. So carefully check. CPU0 has been set up in init
298 * already.
299 */
300 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
301 return 0;
302
303 /* Use the static page for the first CPUs, allocate otherwise */
304 if (cpu < HVC_BOOT_ARRAY_SIZE)
305 p = &hv_clock_boot[cpu];
306 else if (hvclock_mem)
307 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
308 else
309 return -ENOMEM;
310
311 per_cpu(hv_clock_per_cpu, cpu) = p;
312 return p ? 0 : -ENOMEM;
313}
314
315void __init kvmclock_init(void)
316{
317 u8 flags;
318
319 if (!kvm_para_available() || !kvmclock)
320 return;
321
322 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
323 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
324 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
325 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
326 return;
327 }
328
329 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
330 kvmclock_setup_percpu, NULL) < 0) {
331 return;
332 }
333
334 pr_info("kvm-clock: Using msrs %x and %x",
335 msr_kvm_system_time, msr_kvm_wall_clock);
336
337 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
338 kvm_register_clock("primary cpu clock");
339 pvclock_set_pvti_cpu0_va(hv_clock_boot);
340
341 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
342 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
343
344 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
345 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
346
347 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
348 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
349 x86_platform.get_wallclock = kvm_get_wallclock;
350 x86_platform.set_wallclock = kvm_set_wallclock;
351#ifdef CONFIG_X86_LOCAL_APIC
352 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
353#endif
354 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
355 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
356 machine_ops.shutdown = kvm_shutdown;
357#ifdef CONFIG_KEXEC_CORE
358 machine_ops.crash_shutdown = kvm_crash_shutdown;
359#endif
360 kvm_get_preset_lpj();
361
362 /*
363 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
364 * with P/T states and does not stop in deep C-states.
365 *
366 * Invariant TSC exposed by host means kvmclock is not necessary:
367 * can use TSC as clocksource.
368 *
369 */
370 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
371 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
372 !check_tsc_unstable())
373 kvm_clock.rating = 299;
374
375 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
376 pv_info.name = "KVM";
377}