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 #include <linux/cc_platform.h>
20
21 #include <asm/hypervisor.h>
22 #include <asm/timer.h>
23 #include <asm/x86_init.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;
29 static int msr_kvm_wall_clock __ro_after_init;
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 what's mapped via vsyscalls to userspace */
47 #define HVC_BOOT_ARRAY_SIZE \
48 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
49
50 static struct pvclock_vsyscall_time_info
51 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
52 static struct pvclock_wall_clock wall_clock __bss_decrypted;
53 static struct pvclock_vsyscall_time_info *hvclock_mem;
54 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
55 EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu);
56
57 /*
58 * The wallclock is the time of day when we booted. Since then, some time may
59 * have elapsed since the hypervisor wrote the data. So we try to account for
60 * that with system time
61 */
kvm_get_wallclock(struct timespec64 * now)62 static void kvm_get_wallclock(struct timespec64 *now)
63 {
64 wrmsrq(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
65 preempt_disable();
66 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
67 preempt_enable();
68 }
69
kvm_set_wallclock(const struct timespec64 * now)70 static int kvm_set_wallclock(const struct timespec64 *now)
71 {
72 return -ENODEV;
73 }
74
kvm_clock_read(void)75 static u64 kvm_clock_read(void)
76 {
77 u64 ret;
78
79 preempt_disable_notrace();
80 ret = pvclock_clocksource_read_nowd(this_cpu_pvti());
81 preempt_enable_notrace();
82 return ret;
83 }
84
kvm_clock_get_cycles(struct clocksource * cs)85 static u64 kvm_clock_get_cycles(struct clocksource *cs)
86 {
87 return kvm_clock_read();
88 }
89
kvm_sched_clock_read(void)90 static noinstr u64 kvm_sched_clock_read(void)
91 {
92 return pvclock_clocksource_read_nowd(this_cpu_pvti()) - kvm_sched_clock_offset;
93 }
94
kvm_sched_clock_init(bool stable)95 static inline void kvm_sched_clock_init(bool stable)
96 {
97 if (!stable)
98 clear_sched_clock_stable();
99 kvm_sched_clock_offset = kvm_clock_read();
100 paravirt_set_sched_clock(kvm_sched_clock_read);
101
102 pr_info("kvm-clock: using sched offset of %llu cycles",
103 kvm_sched_clock_offset);
104
105 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
106 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
107 }
108
109 /*
110 * If we don't do that, there is the possibility that the guest
111 * will calibrate under heavy load - thus, getting a lower lpj -
112 * and execute the delays themselves without load. This is wrong,
113 * because no delay loop can finish beforehand.
114 * Any heuristics is subject to fail, because ultimately, a large
115 * poll of guests can be running and trouble each other. So we preset
116 * lpj here
117 */
kvm_get_tsc_khz(void)118 static unsigned long kvm_get_tsc_khz(void)
119 {
120 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
121 return pvclock_tsc_khz(this_cpu_pvti());
122 }
123
kvm_get_preset_lpj(void)124 static void __init kvm_get_preset_lpj(void)
125 {
126 unsigned long khz;
127 u64 lpj;
128
129 khz = kvm_get_tsc_khz();
130
131 lpj = ((u64)khz * 1000);
132 do_div(lpj, HZ);
133 preset_lpj = lpj;
134 }
135
kvm_check_and_clear_guest_paused(void)136 bool kvm_check_and_clear_guest_paused(void)
137 {
138 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
139 bool ret = false;
140
141 if (!src)
142 return ret;
143
144 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
145 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
146 pvclock_touch_watchdogs();
147 ret = true;
148 }
149 return ret;
150 }
151
kvm_cs_enable(struct clocksource * cs)152 static int kvm_cs_enable(struct clocksource *cs)
153 {
154 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
155 return 0;
156 }
157
158 static struct clocksource kvm_clock = {
159 .name = "kvm-clock",
160 .read = kvm_clock_get_cycles,
161 .rating = 400,
162 .mask = CLOCKSOURCE_MASK(64),
163 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
164 .id = CSID_X86_KVM_CLK,
165 .enable = kvm_cs_enable,
166 };
167
kvm_register_clock(char * txt)168 static void kvm_register_clock(char *txt)
169 {
170 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
171 u64 pa;
172
173 if (!src)
174 return;
175
176 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
177 wrmsrq(msr_kvm_system_time, pa);
178 pr_debug("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
179 }
180
kvm_save_sched_clock_state(void)181 static void kvm_save_sched_clock_state(void)
182 {
183 }
184
kvm_restore_sched_clock_state(void)185 static void kvm_restore_sched_clock_state(void)
186 {
187 kvm_register_clock("primary cpu clock, resume");
188 }
189
190 #ifdef CONFIG_X86_LOCAL_APIC
kvm_setup_secondary_clock(void)191 static void kvm_setup_secondary_clock(void)
192 {
193 kvm_register_clock("secondary cpu clock");
194 }
195 #endif
196
kvmclock_disable(void)197 void kvmclock_disable(void)
198 {
199 if (msr_kvm_system_time)
200 native_write_msr(msr_kvm_system_time, 0);
201 }
202
kvmclock_init_mem(void)203 static void __init kvmclock_init_mem(void)
204 {
205 unsigned long ncpus;
206 unsigned int order;
207 struct page *p;
208 int r;
209
210 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
211 return;
212
213 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
214 order = get_order(ncpus * sizeof(*hvclock_mem));
215
216 p = alloc_pages(GFP_KERNEL, order);
217 if (!p) {
218 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
219 return;
220 }
221
222 hvclock_mem = page_address(p);
223
224 /*
225 * hvclock is shared between the guest and the hypervisor, must
226 * be mapped decrypted.
227 */
228 if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
229 r = set_memory_decrypted((unsigned long) hvclock_mem,
230 1UL << order);
231 if (r) {
232 __free_pages(p, order);
233 hvclock_mem = NULL;
234 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
235 return;
236 }
237 }
238
239 memset(hvclock_mem, 0, PAGE_SIZE << order);
240 }
241
kvm_setup_vsyscall_timeinfo(void)242 static int __init kvm_setup_vsyscall_timeinfo(void)
243 {
244 if (!kvm_para_available() || !kvmclock || nopv)
245 return 0;
246
247 kvmclock_init_mem();
248
249 #ifdef CONFIG_X86_64
250 if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
251 u8 flags;
252
253 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
254 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
255 return 0;
256
257 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
258 }
259 #endif
260
261 return 0;
262 }
263 early_initcall(kvm_setup_vsyscall_timeinfo);
264
kvmclock_setup_percpu(unsigned int cpu)265 static int kvmclock_setup_percpu(unsigned int cpu)
266 {
267 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
268
269 /*
270 * The per cpu area setup replicates CPU0 data to all cpu
271 * pointers. So carefully check. CPU0 has been set up in init
272 * already.
273 */
274 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
275 return 0;
276
277 /* Use the static page for the first CPUs, allocate otherwise */
278 if (cpu < HVC_BOOT_ARRAY_SIZE)
279 p = &hv_clock_boot[cpu];
280 else if (hvclock_mem)
281 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
282 else
283 return -ENOMEM;
284
285 per_cpu(hv_clock_per_cpu, cpu) = p;
286 return p ? 0 : -ENOMEM;
287 }
288
kvmclock_init(void)289 void __init kvmclock_init(void)
290 {
291 u8 flags;
292
293 if (!kvm_para_available() || !kvmclock)
294 return;
295
296 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
297 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
298 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
299 } else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
300 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
301 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
302 } else {
303 return;
304 }
305
306 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
307 kvmclock_setup_percpu, NULL) < 0) {
308 return;
309 }
310
311 pr_info("kvm-clock: Using msrs %x and %x",
312 msr_kvm_system_time, msr_kvm_wall_clock);
313
314 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
315 kvm_register_clock("primary cpu clock");
316 pvclock_set_pvti_cpu0_va(hv_clock_boot);
317
318 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
319 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
320
321 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
322 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
323
324 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
325 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
326 x86_platform.get_wallclock = kvm_get_wallclock;
327 x86_platform.set_wallclock = kvm_set_wallclock;
328 #ifdef CONFIG_X86_LOCAL_APIC
329 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
330 #endif
331 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
332 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
333 kvm_get_preset_lpj();
334
335 /*
336 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
337 * with P/T states and does not stop in deep C-states.
338 *
339 * Invariant TSC exposed by host means kvmclock is not necessary:
340 * can use TSC as clocksource.
341 *
342 */
343 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
344 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
345 !check_tsc_unstable())
346 kvm_clock.rating = 299;
347
348 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
349 pv_info.name = "KVM";
350 }
351