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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
26static int kvmclock __initdata = 1;
27static int kvmclock_vsyscall __initdata = 1;
28static int msr_kvm_system_time __ro_after_init;
29static int msr_kvm_wall_clock __ro_after_init;
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 what's mapped via vsyscalls to userspace */
47#define HVC_BOOT_ARRAY_SIZE \
48 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
49
50static struct pvclock_vsyscall_time_info
51 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
52static struct pvclock_wall_clock wall_clock __bss_decrypted;
53static struct pvclock_vsyscall_time_info *hvclock_mem;
54DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
55EXPORT_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 */
62static 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
70static int kvm_set_wallclock(const struct timespec64 *now)
71{
72 return -ENODEV;
73}
74
75static 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
85static u64 kvm_clock_get_cycles(struct clocksource *cs)
86{
87 return kvm_clock_read();
88}
89
90static u64 kvm_clock_get_cycles_snapshot(struct clocksource *cs,
91 struct clocksource_hw_snapshot *chs)
92{
93 struct pvclock_vcpu_time_info *src;
94 unsigned version;
95 u64 ret, tsc;
96
97 preempt_disable_notrace();
98 src = this_cpu_pvti();
99 do {
100 version = pvclock_read_begin(src);
101 tsc = rdtsc_ordered();
102 ret = __pvclock_read_cycles(src, tsc);
103 } while (pvclock_read_retry(src, version));
104 preempt_enable_notrace();
105
106 chs->hw_cycles = tsc;
107 chs->hw_csid = CSID_X86_TSC;
108 return ret;
109}
110
111static noinstr u64 kvm_sched_clock_read(void)
112{
113 return pvclock_clocksource_read_nowd(this_cpu_pvti()) - kvm_sched_clock_offset;
114}
115
116static inline void kvm_sched_clock_init(bool stable)
117{
118 if (!stable)
119 clear_sched_clock_stable();
120 kvm_sched_clock_offset = kvm_clock_read();
121 paravirt_set_sched_clock(kvm_sched_clock_read);
122
123 pr_info("kvm-clock: using sched offset of %llu cycles",
124 kvm_sched_clock_offset);
125
126 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
127 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
128}
129
130/*
131 * If we don't do that, there is the possibility that the guest
132 * will calibrate under heavy load - thus, getting a lower lpj -
133 * and execute the delays themselves without load. This is wrong,
134 * because no delay loop can finish beforehand.
135 * Any heuristics is subject to fail, because ultimately, a large
136 * poll of guests can be running and trouble each other. So we preset
137 * lpj here
138 */
139static unsigned long kvm_get_tsc_khz(void)
140{
141 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
142 return pvclock_tsc_khz(this_cpu_pvti());
143}
144
145static void __init kvm_get_preset_lpj(void)
146{
147 unsigned long khz;
148 u64 lpj;
149
150 khz = kvm_get_tsc_khz();
151
152 lpj = ((u64)khz * 1000);
153 do_div(lpj, HZ);
154 preset_lpj = lpj;
155}
156
157bool kvm_check_and_clear_guest_paused(void)
158{
159 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
160 bool ret = false;
161
162 if (!src)
163 return ret;
164
165 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
166 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
167 pvclock_touch_watchdogs();
168 ret = true;
169 }
170 return ret;
171}
172
173static int kvm_cs_enable(struct clocksource *cs)
174{
175 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
176 return 0;
177}
178
179static struct clocksource kvm_clock = {
180 .name = "kvm-clock",
181 .read = kvm_clock_get_cycles,
182 .read_snapshot = kvm_clock_get_cycles_snapshot,
183 .rating = 400,
184 .mask = CLOCKSOURCE_MASK(64),
185 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
186 .id = CSID_X86_KVM_CLK,
187 .enable = kvm_cs_enable,
188};
189
190static void kvm_register_clock(char *txt)
191{
192 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
193 u64 pa;
194
195 if (!src)
196 return;
197
198 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
199 wrmsrq(msr_kvm_system_time, pa);
200 pr_debug("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
201}
202
203static void kvm_save_sched_clock_state(void)
204{
205}
206
207static void kvm_restore_sched_clock_state(void)
208{
209 kvm_register_clock("primary cpu clock, resume");
210}
211
212#ifdef CONFIG_X86_LOCAL_APIC
213static void kvm_setup_secondary_clock(void)
214{
215 kvm_register_clock("secondary cpu clock");
216}
217#endif
218
219void kvmclock_disable(void)
220{
221 if (msr_kvm_system_time)
222 native_write_msr(msr_kvm_system_time, 0);
223}
224
225static void __init kvmclock_init_mem(void)
226{
227 unsigned long ncpus;
228 unsigned int order;
229 struct page *p;
230 int r;
231
232 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
233 return;
234
235 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
236 order = get_order(ncpus * sizeof(*hvclock_mem));
237
238 p = alloc_pages(GFP_KERNEL, order);
239 if (!p) {
240 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
241 return;
242 }
243
244 hvclock_mem = page_address(p);
245
246 /*
247 * hvclock is shared between the guest and the hypervisor, must
248 * be mapped decrypted.
249 */
250 if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
251 r = set_memory_decrypted((unsigned long) hvclock_mem,
252 1UL << order);
253 if (r) {
254 __free_pages(p, order);
255 hvclock_mem = NULL;
256 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
257 return;
258 }
259 }
260
261 memset(hvclock_mem, 0, PAGE_SIZE << order);
262}
263
264static int __init kvm_setup_vsyscall_timeinfo(void)
265{
266 if (!kvm_para_available() || !kvmclock || nopv)
267 return 0;
268
269 kvmclock_init_mem();
270
271#ifdef CONFIG_X86_64
272 if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
273 u8 flags;
274
275 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
276 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
277 return 0;
278
279 kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
280 }
281#endif
282
283 return 0;
284}
285early_initcall(kvm_setup_vsyscall_timeinfo);
286
287static int kvmclock_setup_percpu(unsigned int cpu)
288{
289 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
290
291 /*
292 * The per cpu area setup replicates CPU0 data to all cpu
293 * pointers. So carefully check. CPU0 has been set up in init
294 * already.
295 */
296 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
297 return 0;
298
299 /* Use the static page for the first CPUs, allocate otherwise */
300 if (cpu < HVC_BOOT_ARRAY_SIZE)
301 p = &hv_clock_boot[cpu];
302 else if (hvclock_mem)
303 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
304 else
305 return -ENOMEM;
306
307 per_cpu(hv_clock_per_cpu, cpu) = p;
308 return p ? 0 : -ENOMEM;
309}
310
311void __init kvmclock_init(void)
312{
313 u8 flags;
314
315 if (!kvm_para_available() || !kvmclock)
316 return;
317
318 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
319 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
320 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
321 } else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
322 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
323 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
324 } else {
325 return;
326 }
327
328 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
329 kvmclock_setup_percpu, NULL) < 0) {
330 return;
331 }
332
333 pr_info("kvm-clock: Using msrs %x and %x",
334 msr_kvm_system_time, msr_kvm_wall_clock);
335
336 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
337 kvm_register_clock("primary cpu clock");
338 pvclock_set_pvti_cpu0_va(hv_clock_boot);
339
340 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
341 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
342
343 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
344 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
345
346 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
347 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
348 x86_platform.get_wallclock = kvm_get_wallclock;
349 x86_platform.set_wallclock = kvm_set_wallclock;
350#ifdef CONFIG_X86_LOCAL_APIC
351 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
352#endif
353 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
354 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
355 kvm_get_preset_lpj();
356
357 /*
358 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
359 * with P/T states and does not stop in deep C-states.
360 *
361 * Invariant TSC exposed by host means kvmclock is not necessary:
362 * can use TSC as clocksource.
363 *
364 */
365 if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
366 boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
367 !check_tsc_unstable())
368 kvm_clock.rating = 299;
369
370 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
371 pv_info.name = "KVM";
372}