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