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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 
20 #include <asm/hypervisor.h>
21 #include <asm/mem_encrypt.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 
parse_no_kvmclock(char * arg)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 
parse_no_kvmclock_vsyscall(char * arg)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 whats mapped via vsyscalls to userspace */
46 #define HV_CLOCK_SIZE	(sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS)
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 	wrmsrl(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(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 u64 kvm_sched_clock_read(void)
91 {
92 	return kvm_clock_read() - 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 	pv_ops.time.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 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 	.enable	= kvm_cs_enable,
165 };
166 EXPORT_SYMBOL_GPL(kvm_clock);
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 	wrmsrl(msr_kvm_system_time, pa);
178 	pr_info("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, 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 (sev_active()) {
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 	kvmclock_init_mem();
245 
246 #ifdef CONFIG_X86_64
247 	if (per_cpu(hv_clock_per_cpu, 0) && kvmclock_vsyscall) {
248 		u8 flags;
249 
250 		flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
251 		if (!(flags & PVCLOCK_TSC_STABLE_BIT))
252 			return 0;
253 
254 		kvm_clock.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
255 	}
256 #endif
257 
258 	return 0;
259 }
260 early_initcall(kvm_setup_vsyscall_timeinfo);
261 
kvmclock_setup_percpu(unsigned int cpu)262 static int kvmclock_setup_percpu(unsigned int cpu)
263 {
264 	struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
265 
266 	/*
267 	 * The per cpu area setup replicates CPU0 data to all cpu
268 	 * pointers. So carefully check. CPU0 has been set up in init
269 	 * already.
270 	 */
271 	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
272 		return 0;
273 
274 	/* Use the static page for the first CPUs, allocate otherwise */
275 	if (cpu < HVC_BOOT_ARRAY_SIZE)
276 		p = &hv_clock_boot[cpu];
277 	else if (hvclock_mem)
278 		p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
279 	else
280 		return -ENOMEM;
281 
282 	per_cpu(hv_clock_per_cpu, cpu) = p;
283 	return p ? 0 : -ENOMEM;
284 }
285 
kvmclock_init(void)286 void __init kvmclock_init(void)
287 {
288 	u8 flags;
289 
290 	if (!kvm_para_available() || !kvmclock)
291 		return;
292 
293 	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
294 		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
295 		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
296 	} else if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
297 		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
298 		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
299 	} else {
300 		return;
301 	}
302 
303 	if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
304 			      kvmclock_setup_percpu, NULL) < 0) {
305 		return;
306 	}
307 
308 	pr_info("kvm-clock: Using msrs %x and %x",
309 		msr_kvm_system_time, msr_kvm_wall_clock);
310 
311 	this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
312 	kvm_register_clock("primary cpu clock");
313 	pvclock_set_pvti_cpu0_va(hv_clock_boot);
314 
315 	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
316 		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
317 
318 	flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
319 	kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
320 
321 	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
322 	x86_platform.calibrate_cpu = kvm_get_tsc_khz;
323 	x86_platform.get_wallclock = kvm_get_wallclock;
324 	x86_platform.set_wallclock = kvm_set_wallclock;
325 #ifdef CONFIG_X86_LOCAL_APIC
326 	x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
327 #endif
328 	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
329 	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
330 	kvm_get_preset_lpj();
331 
332 	/*
333 	 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
334 	 * with P/T states and does not stop in deep C-states.
335 	 *
336 	 * Invariant TSC exposed by host means kvmclock is not necessary:
337 	 * can use TSC as clocksource.
338 	 *
339 	 */
340 	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
341 	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
342 	    !check_tsc_unstable())
343 		kvm_clock.rating = 299;
344 
345 	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
346 	pv_info.name = "KVM";
347 }
348