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
162struct clocksource kvm_clock = {
163 .name = "kvm-clock",
164 .read = kvm_clock_get_cycles,
165 .rating = 400,
166 .mask = CLOCKSOURCE_MASK(64),
167 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
168};
169EXPORT_SYMBOL_GPL(kvm_clock);
170
171static void kvm_register_clock(char *txt)
172{
173 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
174 u64 pa;
175
176 if (!src)
177 return;
178
179 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
180 wrmsrl(msr_kvm_system_time, pa);
181 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
182}
183
184static void kvm_save_sched_clock_state(void)
185{
186}
187
188static void kvm_restore_sched_clock_state(void)
189{
190 kvm_register_clock("primary cpu clock, resume");
191}
192
193#ifdef CONFIG_X86_LOCAL_APIC
194static void kvm_setup_secondary_clock(void)
195{
196 kvm_register_clock("secondary cpu clock");
197}
198#endif
199
200/*
201 * After the clock is registered, the host will keep writing to the
202 * registered memory location. If the guest happens to shutdown, this memory
203 * won't be valid. In cases like kexec, in which you install a new kernel, this
204 * means a random memory location will be kept being written. So before any
205 * kind of shutdown from our side, we unregister the clock by writing anything
206 * that does not have the 'enable' bit set in the msr
207 */
208#ifdef CONFIG_KEXEC_CORE
209static void kvm_crash_shutdown(struct pt_regs *regs)
210{
211 native_write_msr(msr_kvm_system_time, 0, 0);
212 kvm_disable_steal_time();
213 native_machine_crash_shutdown(regs);
214}
215#endif
216
217static void kvm_shutdown(void)
218{
219 native_write_msr(msr_kvm_system_time, 0, 0);
220 kvm_disable_steal_time();
221 native_machine_shutdown();
222}
223
224static void __init kvmclock_init_mem(void)
225{
226 unsigned long ncpus;
227 unsigned int order;
228 struct page *p;
229 int r;
230
231 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
232 return;
233
234 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
235 order = get_order(ncpus * sizeof(*hvclock_mem));
236
237 p = alloc_pages(GFP_KERNEL, order);
238 if (!p) {
239 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
240 return;
241 }
242
243 hvclock_mem = page_address(p);
244
245 /*
246 * hvclock is shared between the guest and the hypervisor, must
247 * be mapped decrypted.
248 */
249 if (sev_active()) {
250 r = set_memory_decrypted((unsigned long) hvclock_mem,
251 1UL << order);
252 if (r) {
253 __free_pages(p, order);
254 hvclock_mem = NULL;
255 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
256 return;
257 }
258 }
259
260 memset(hvclock_mem, 0, PAGE_SIZE << order);
261}
262
263static int __init kvm_setup_vsyscall_timeinfo(void)
264{
265#ifdef CONFIG_X86_64
266 u8 flags;
267
268 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall)
269 return 0;
270
271 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
272 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
273 return 0;
274
275 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
276#endif
277
278 kvmclock_init_mem();
279
280 return 0;
281}
282early_initcall(kvm_setup_vsyscall_timeinfo);
283
284static int kvmclock_setup_percpu(unsigned int cpu)
285{
286 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
287
288 /*
289 * The per cpu area setup replicates CPU0 data to all cpu
290 * pointers. So carefully check. CPU0 has been set up in init
291 * already.
292 */
293 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
294 return 0;
295
296 /* Use the static page for the first CPUs, allocate otherwise */
297 if (cpu < HVC_BOOT_ARRAY_SIZE)
298 p = &hv_clock_boot[cpu];
299 else if (hvclock_mem)
300 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
301 else
302 return -ENOMEM;
303
304 per_cpu(hv_clock_per_cpu, cpu) = p;
305 return p ? 0 : -ENOMEM;
306}
307
308void __init kvmclock_init(void)
309{
310 u8 flags;
311
312 if (!kvm_para_available() || !kvmclock)
313 return;
314
315 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
316 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
317 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
318 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
319 return;
320 }
321
322 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
323 kvmclock_setup_percpu, NULL) < 0) {
324 return;
325 }
326
327 pr_info("kvm-clock: Using msrs %x and %x",
328 msr_kvm_system_time, msr_kvm_wall_clock);
329
330 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
331 kvm_register_clock("primary cpu clock");
332 pvclock_set_pvti_cpu0_va(hv_clock_boot);
333
334 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
335 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
336
337 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
338 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
339
340 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
341 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
342 x86_platform.get_wallclock = kvm_get_wallclock;
343 x86_platform.set_wallclock = kvm_set_wallclock;
344#ifdef CONFIG_X86_LOCAL_APIC
345 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
346#endif
347 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
348 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
349 machine_ops.shutdown = kvm_shutdown;
350#ifdef CONFIG_KEXEC_CORE
351 machine_ops.crash_shutdown = kvm_crash_shutdown;
352#endif
353 kvm_get_preset_lpj();
354
355 /*
356 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
357 * with P/T states and does not stop in deep C-states.
358 *
359 * Invariant TSC exposed by host means kvmclock is not necessary:
360 * can use TSC as clocksource.
361 *
362 */
363 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
364 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
365 !check_tsc_unstable())
366 kvm_clock.rating = 299;
367
368 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
369 pv_info.name = "KVM";
370}
371