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
26 static int kvmclock __initdata = 1;
27 static int kvmclock_vsyscall __initdata = 1;
28 static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME;
29 static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK;
30 static u64 kvm_sched_clock_offset __ro_after_init;
31
parse_no_kvmclock(char * arg)32 static int __init parse_no_kvmclock(char *arg)
33 {
34 kvmclock = 0;
35 return 0;
36 }
37 early_param("no-kvmclock", parse_no_kvmclock);
38
parse_no_kvmclock_vsyscall(char * arg)39 static int __init parse_no_kvmclock_vsyscall(char *arg)
40 {
41 kvmclock_vsyscall = 0;
42 return 0;
43 }
44 early_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
51 static struct pvclock_vsyscall_time_info
52 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
53 static struct pvclock_wall_clock wall_clock __bss_decrypted;
54 static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
55 static struct pvclock_vsyscall_time_info *hvclock_mem;
56
this_cpu_pvti(void)57 static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void)
58 {
59 return &this_cpu_read(hv_clock_per_cpu)->pvti;
60 }
61
this_cpu_hvclock(void)62 static 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 */
kvm_get_wallclock(struct timespec64 * now)72 static 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
kvm_set_wallclock(const struct timespec64 * now)80 static int kvm_set_wallclock(const struct timespec64 *now)
81 {
82 return -ENODEV;
83 }
84
kvm_clock_read(void)85 static 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
kvm_clock_get_cycles(struct clocksource * cs)95 static u64 kvm_clock_get_cycles(struct clocksource *cs)
96 {
97 return kvm_clock_read();
98 }
99
kvm_sched_clock_read(void)100 static u64 kvm_sched_clock_read(void)
101 {
102 return kvm_clock_read() - kvm_sched_clock_offset;
103 }
104
kvm_sched_clock_init(bool stable)105 static 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 */
kvm_get_tsc_khz(void)128 static 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
kvm_get_preset_lpj(void)134 static 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
kvm_check_and_clear_guest_paused(void)146 bool 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
kvm_cs_enable(struct clocksource * cs)162 static int kvm_cs_enable(struct clocksource *cs)
163 {
164 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
165 return 0;
166 }
167
168 struct 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 };
176 EXPORT_SYMBOL_GPL(kvm_clock);
177
kvm_register_clock(char * txt)178 static 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
kvm_save_sched_clock_state(void)191 static void kvm_save_sched_clock_state(void)
192 {
193 }
194
kvm_restore_sched_clock_state(void)195 static void kvm_restore_sched_clock_state(void)
196 {
197 kvm_register_clock("primary cpu clock, resume");
198 }
199
200 #ifdef CONFIG_X86_LOCAL_APIC
kvm_setup_secondary_clock(void)201 static 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
kvm_crash_shutdown(struct pt_regs * regs)216 static 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
kvm_shutdown(void)224 static 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
kvmclock_init_mem(void)231 static 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
kvm_setup_vsyscall_timeinfo(void)270 static 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 }
289 early_initcall(kvm_setup_vsyscall_timeinfo);
290
kvmclock_setup_percpu(unsigned int cpu)291 static 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
kvmclock_init(void)315 void __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 }
378
