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/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; |
28 | static int msr_kvm_wall_clock __ro_after_init; |
29 | static u64 kvm_sched_clock_offset __ro_after_init; |
30 | |
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 | |
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 what's 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 struct pvclock_vsyscall_time_info *hvclock_mem; |
53 | DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu); |
54 | EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu); |
55 | |
56 | /* |
57 | * The wallclock is the time of day when we booted. Since then, some time may |
58 | * have elapsed since the hypervisor wrote the data. So we try to account for |
59 | * that with system time |
60 | */ |
61 | static void kvm_get_wallclock(struct timespec64 *now) |
62 | { |
63 | wrmsrl(msr: msr_kvm_wall_clock, val: slow_virt_to_phys(address: &wall_clock)); |
64 | preempt_disable(); |
65 | pvclock_read_wallclock(wall: &wall_clock, vcpu: this_cpu_pvti(), ts: now); |
66 | preempt_enable(); |
67 | } |
68 | |
69 | static int kvm_set_wallclock(const struct timespec64 *now) |
70 | { |
71 | return -ENODEV; |
72 | } |
73 | |
74 | static u64 kvm_clock_read(void) |
75 | { |
76 | u64 ret; |
77 | |
78 | preempt_disable_notrace(); |
79 | ret = pvclock_clocksource_read_nowd(src: this_cpu_pvti()); |
80 | preempt_enable_notrace(); |
81 | return ret; |
82 | } |
83 | |
84 | static u64 kvm_clock_get_cycles(struct clocksource *cs) |
85 | { |
86 | return kvm_clock_read(); |
87 | } |
88 | |
89 | static noinstr u64 kvm_sched_clock_read(void) |
90 | { |
91 | return pvclock_clocksource_read_nowd(src: this_cpu_pvti()) - kvm_sched_clock_offset; |
92 | } |
93 | |
94 | static inline void kvm_sched_clock_init(bool stable) |
95 | { |
96 | if (!stable) |
97 | clear_sched_clock_stable(); |
98 | kvm_sched_clock_offset = kvm_clock_read(); |
99 | paravirt_set_sched_clock(func: kvm_sched_clock_read); |
100 | |
101 | pr_info("kvm-clock: using sched offset of %llu cycles" , |
102 | kvm_sched_clock_offset); |
103 | |
104 | BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) > |
105 | sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time)); |
106 | } |
107 | |
108 | /* |
109 | * If we don't do that, there is the possibility that the guest |
110 | * will calibrate under heavy load - thus, getting a lower lpj - |
111 | * and execute the delays themselves without load. This is wrong, |
112 | * because no delay loop can finish beforehand. |
113 | * Any heuristics is subject to fail, because ultimately, a large |
114 | * poll of guests can be running and trouble each other. So we preset |
115 | * lpj here |
116 | */ |
117 | static unsigned long kvm_get_tsc_khz(void) |
118 | { |
119 | setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); |
120 | return pvclock_tsc_khz(src: this_cpu_pvti()); |
121 | } |
122 | |
123 | static void __init kvm_get_preset_lpj(void) |
124 | { |
125 | unsigned long khz; |
126 | u64 lpj; |
127 | |
128 | khz = kvm_get_tsc_khz(); |
129 | |
130 | lpj = ((u64)khz * 1000); |
131 | do_div(lpj, HZ); |
132 | preset_lpj = lpj; |
133 | } |
134 | |
135 | bool kvm_check_and_clear_guest_paused(void) |
136 | { |
137 | struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); |
138 | bool ret = false; |
139 | |
140 | if (!src) |
141 | return ret; |
142 | |
143 | if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) { |
144 | src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED; |
145 | pvclock_touch_watchdogs(); |
146 | ret = true; |
147 | } |
148 | return ret; |
149 | } |
150 | |
151 | static int kvm_cs_enable(struct clocksource *cs) |
152 | { |
153 | vclocks_set_used(which: VDSO_CLOCKMODE_PVCLOCK); |
154 | return 0; |
155 | } |
156 | |
157 | static struct clocksource kvm_clock = { |
158 | .name = "kvm-clock" , |
159 | .read = kvm_clock_get_cycles, |
160 | .rating = 400, |
161 | .mask = CLOCKSOURCE_MASK(64), |
162 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
163 | .id = CSID_X86_KVM_CLK, |
164 | .enable = kvm_cs_enable, |
165 | }; |
166 | |
167 | static void kvm_register_clock(char *txt) |
168 | { |
169 | struct pvclock_vsyscall_time_info *src = this_cpu_hvclock(); |
170 | u64 pa; |
171 | |
172 | if (!src) |
173 | return; |
174 | |
175 | pa = slow_virt_to_phys(address: &src->pvti) | 0x01ULL; |
176 | wrmsrl(msr: msr_kvm_system_time, val: pa); |
177 | pr_debug("kvm-clock: cpu %d, msr %llx, %s" , smp_processor_id(), pa, txt); |
178 | } |
179 | |
180 | static void kvm_save_sched_clock_state(void) |
181 | { |
182 | } |
183 | |
184 | static void kvm_restore_sched_clock_state(void) |
185 | { |
186 | kvm_register_clock(txt: "primary cpu clock, resume" ); |
187 | } |
188 | |
189 | #ifdef CONFIG_X86_LOCAL_APIC |
190 | static void kvm_setup_secondary_clock(void) |
191 | { |
192 | kvm_register_clock(txt: "secondary cpu clock" ); |
193 | } |
194 | #endif |
195 | |
196 | void kvmclock_disable(void) |
197 | { |
198 | if (msr_kvm_system_time) |
199 | native_write_msr(msr: msr_kvm_system_time, low: 0, high: 0); |
200 | } |
201 | |
202 | static void __init kvmclock_init_mem(void) |
203 | { |
204 | unsigned long ncpus; |
205 | unsigned int order; |
206 | struct page *p; |
207 | int r; |
208 | |
209 | if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus()) |
210 | return; |
211 | |
212 | ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE; |
213 | order = get_order(size: ncpus * sizeof(*hvclock_mem)); |
214 | |
215 | p = alloc_pages(GFP_KERNEL, order); |
216 | if (!p) { |
217 | pr_warn("%s: failed to alloc %d pages" , __func__, (1U << order)); |
218 | return; |
219 | } |
220 | |
221 | hvclock_mem = page_address(p); |
222 | |
223 | /* |
224 | * hvclock is shared between the guest and the hypervisor, must |
225 | * be mapped decrypted. |
226 | */ |
227 | if (cc_platform_has(attr: CC_ATTR_GUEST_MEM_ENCRYPT)) { |
228 | r = set_memory_decrypted(addr: (unsigned long) hvclock_mem, |
229 | numpages: 1UL << order); |
230 | if (r) { |
231 | __free_pages(page: p, order); |
232 | hvclock_mem = NULL; |
233 | pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n" ); |
234 | return; |
235 | } |
236 | } |
237 | |
238 | memset(hvclock_mem, 0, PAGE_SIZE << order); |
239 | } |
240 | |
241 | static int __init kvm_setup_vsyscall_timeinfo(void) |
242 | { |
243 | if (!kvm_para_available() || !kvmclock || nopv) |
244 | return 0; |
245 | |
246 | kvmclock_init_mem(); |
247 | |
248 | #ifdef CONFIG_X86_64 |
249 | if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) { |
250 | u8 flags; |
251 | |
252 | flags = pvclock_read_flags(src: &hv_clock_boot[0].pvti); |
253 | if (!(flags & PVCLOCK_TSC_STABLE_BIT)) |
254 | return 0; |
255 | |
256 | kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK; |
257 | } |
258 | #endif |
259 | |
260 | return 0; |
261 | } |
262 | early_initcall(kvm_setup_vsyscall_timeinfo); |
263 | |
264 | static int kvmclock_setup_percpu(unsigned int cpu) |
265 | { |
266 | struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu); |
267 | |
268 | /* |
269 | * The per cpu area setup replicates CPU0 data to all cpu |
270 | * pointers. So carefully check. CPU0 has been set up in init |
271 | * already. |
272 | */ |
273 | if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0))) |
274 | return 0; |
275 | |
276 | /* Use the static page for the first CPUs, allocate otherwise */ |
277 | if (cpu < HVC_BOOT_ARRAY_SIZE) |
278 | p = &hv_clock_boot[cpu]; |
279 | else if (hvclock_mem) |
280 | p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE; |
281 | else |
282 | return -ENOMEM; |
283 | |
284 | per_cpu(hv_clock_per_cpu, cpu) = p; |
285 | return p ? 0 : -ENOMEM; |
286 | } |
287 | |
288 | void __init kvmclock_init(void) |
289 | { |
290 | u8 flags; |
291 | |
292 | if (!kvm_para_available() || !kvmclock) |
293 | return; |
294 | |
295 | if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) { |
296 | msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW; |
297 | msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW; |
298 | } else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) { |
299 | msr_kvm_system_time = MSR_KVM_SYSTEM_TIME; |
300 | msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK; |
301 | } else { |
302 | return; |
303 | } |
304 | |
305 | if (cpuhp_setup_state(state: CPUHP_BP_PREPARE_DYN, name: "kvmclock:setup_percpu" , |
306 | startup: kvmclock_setup_percpu, NULL) < 0) { |
307 | return; |
308 | } |
309 | |
310 | pr_info("kvm-clock: Using msrs %x and %x" , |
311 | msr_kvm_system_time, msr_kvm_wall_clock); |
312 | |
313 | this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); |
314 | kvm_register_clock(txt: "primary cpu clock" ); |
315 | pvclock_set_pvti_cpu0_va(pvti: hv_clock_boot); |
316 | |
317 | if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) |
318 | pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT); |
319 | |
320 | flags = pvclock_read_flags(src: &hv_clock_boot[0].pvti); |
321 | kvm_sched_clock_init(stable: flags & PVCLOCK_TSC_STABLE_BIT); |
322 | |
323 | x86_platform.calibrate_tsc = kvm_get_tsc_khz; |
324 | x86_platform.calibrate_cpu = kvm_get_tsc_khz; |
325 | x86_platform.get_wallclock = kvm_get_wallclock; |
326 | x86_platform.set_wallclock = kvm_set_wallclock; |
327 | #ifdef CONFIG_X86_LOCAL_APIC |
328 | x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock; |
329 | #endif |
330 | x86_platform.save_sched_clock_state = kvm_save_sched_clock_state; |
331 | x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state; |
332 | kvm_get_preset_lpj(); |
333 | |
334 | /* |
335 | * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate |
336 | * with P/T states and does not stop in deep C-states. |
337 | * |
338 | * Invariant TSC exposed by host means kvmclock is not necessary: |
339 | * can use TSC as clocksource. |
340 | * |
341 | */ |
342 | if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && |
343 | boot_cpu_has(X86_FEATURE_NONSTOP_TSC) && |
344 | !check_tsc_unstable()) |
345 | kvm_clock.rating = 299; |
346 | |
347 | clocksource_register_hz(cs: &kvm_clock, NSEC_PER_SEC); |
348 | pv_info.name = "KVM" ; |
349 | } |
350 | |