1 /* KVM paravirtual clock driver. A clocksource implementation
2 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
3
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
8
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
17 */
18
19 #include <linux/clocksource.h>
20 #include <linux/kvm_para.h>
21 #include <asm/pvclock.h>
22 #include <asm/msr.h>
23 #include <asm/apic.h>
24 #include <linux/percpu.h>
25 #include <linux/hardirq.h>
26 #include <linux/cpuhotplug.h>
27 #include <linux/sched.h>
28 #include <linux/sched/clock.h>
29 #include <linux/mm.h>
30 #include <linux/slab.h>
31 #include <linux/set_memory.h>
32
33 #include <asm/hypervisor.h>
34 #include <asm/mem_encrypt.h>
35 #include <asm/x86_init.h>
36 #include <asm/reboot.h>
37 #include <asm/kvmclock.h>
38
39 static int kvmclock __initdata = 1;
40 static int kvmclock_vsyscall __initdata = 1;
41 static int msr_kvm_system_time __ro_after_init = MSR_KVM_SYSTEM_TIME;
42 static int msr_kvm_wall_clock __ro_after_init = MSR_KVM_WALL_CLOCK;
43 static u64 kvm_sched_clock_offset __ro_after_init;
44
parse_no_kvmclock(char * arg)45 static int __init parse_no_kvmclock(char *arg)
46 {
47 kvmclock = 0;
48 return 0;
49 }
50 early_param("no-kvmclock", parse_no_kvmclock);
51
parse_no_kvmclock_vsyscall(char * arg)52 static int __init parse_no_kvmclock_vsyscall(char *arg)
53 {
54 kvmclock_vsyscall = 0;
55 return 0;
56 }
57 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
58
59 /* Aligned to page sizes to match whats mapped via vsyscalls to userspace */
60 #define HV_CLOCK_SIZE (sizeof(struct pvclock_vsyscall_time_info) * NR_CPUS)
61 #define HVC_BOOT_ARRAY_SIZE \
62 (PAGE_SIZE / sizeof(struct pvclock_vsyscall_time_info))
63
64 static struct pvclock_vsyscall_time_info
65 hv_clock_boot[HVC_BOOT_ARRAY_SIZE] __bss_decrypted __aligned(PAGE_SIZE);
66 static struct pvclock_wall_clock wall_clock __bss_decrypted;
67 static DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
68 static struct pvclock_vsyscall_time_info *hvclock_mem;
69
this_cpu_pvti(void)70 static inline struct pvclock_vcpu_time_info *this_cpu_pvti(void)
71 {
72 return &this_cpu_read(hv_clock_per_cpu)->pvti;
73 }
74
this_cpu_hvclock(void)75 static inline struct pvclock_vsyscall_time_info *this_cpu_hvclock(void)
76 {
77 return this_cpu_read(hv_clock_per_cpu);
78 }
79
80 /*
81 * The wallclock is the time of day when we booted. Since then, some time may
82 * have elapsed since the hypervisor wrote the data. So we try to account for
83 * that with system time
84 */
kvm_get_wallclock(struct timespec64 * now)85 static void kvm_get_wallclock(struct timespec64 *now)
86 {
87 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
88 preempt_disable();
89 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
90 preempt_enable();
91 }
92
kvm_set_wallclock(const struct timespec64 * now)93 static int kvm_set_wallclock(const struct timespec64 *now)
94 {
95 return -ENODEV;
96 }
97
kvm_clock_read(void)98 static u64 kvm_clock_read(void)
99 {
100 u64 ret;
101
102 preempt_disable_notrace();
103 ret = pvclock_clocksource_read(this_cpu_pvti());
104 preempt_enable_notrace();
105 return ret;
106 }
107
kvm_clock_get_cycles(struct clocksource * cs)108 static u64 kvm_clock_get_cycles(struct clocksource *cs)
109 {
110 return kvm_clock_read();
111 }
112
kvm_sched_clock_read(void)113 static u64 kvm_sched_clock_read(void)
114 {
115 return kvm_clock_read() - kvm_sched_clock_offset;
116 }
117
kvm_sched_clock_init(bool stable)118 static inline void kvm_sched_clock_init(bool stable)
119 {
120 if (!stable) {
121 pv_time_ops.sched_clock = kvm_clock_read;
122 clear_sched_clock_stable();
123 return;
124 }
125
126 kvm_sched_clock_offset = kvm_clock_read();
127 pv_time_ops.sched_clock = kvm_sched_clock_read;
128
129 pr_info("kvm-clock: using sched offset of %llu cycles",
130 kvm_sched_clock_offset);
131
132 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
133 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
134 }
135
136 /*
137 * If we don't do that, there is the possibility that the guest
138 * will calibrate under heavy load - thus, getting a lower lpj -
139 * and execute the delays themselves without load. This is wrong,
140 * because no delay loop can finish beforehand.
141 * Any heuristics is subject to fail, because ultimately, a large
142 * poll of guests can be running and trouble each other. So we preset
143 * lpj here
144 */
kvm_get_tsc_khz(void)145 static unsigned long kvm_get_tsc_khz(void)
146 {
147 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
148 return pvclock_tsc_khz(this_cpu_pvti());
149 }
150
kvm_get_preset_lpj(void)151 static void __init kvm_get_preset_lpj(void)
152 {
153 unsigned long khz;
154 u64 lpj;
155
156 khz = kvm_get_tsc_khz();
157
158 lpj = ((u64)khz * 1000);
159 do_div(lpj, HZ);
160 preset_lpj = lpj;
161 }
162
kvm_check_and_clear_guest_paused(void)163 bool kvm_check_and_clear_guest_paused(void)
164 {
165 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
166 bool ret = false;
167
168 if (!src)
169 return ret;
170
171 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
172 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
173 pvclock_touch_watchdogs();
174 ret = true;
175 }
176 return ret;
177 }
178
179 struct clocksource kvm_clock = {
180 .name = "kvm-clock",
181 .read = kvm_clock_get_cycles,
182 .rating = 400,
183 .mask = CLOCKSOURCE_MASK(64),
184 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
185 };
186 EXPORT_SYMBOL_GPL(kvm_clock);
187
kvm_register_clock(char * txt)188 static void kvm_register_clock(char *txt)
189 {
190 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
191 u64 pa;
192
193 if (!src)
194 return;
195
196 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
197 wrmsrl(msr_kvm_system_time, pa);
198 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
199 }
200
kvm_save_sched_clock_state(void)201 static void kvm_save_sched_clock_state(void)
202 {
203 }
204
kvm_restore_sched_clock_state(void)205 static void kvm_restore_sched_clock_state(void)
206 {
207 kvm_register_clock("primary cpu clock, resume");
208 }
209
210 #ifdef CONFIG_X86_LOCAL_APIC
kvm_setup_secondary_clock(void)211 static void kvm_setup_secondary_clock(void)
212 {
213 kvm_register_clock("secondary cpu clock");
214 }
215 #endif
216
217 /*
218 * After the clock is registered, the host will keep writing to the
219 * registered memory location. If the guest happens to shutdown, this memory
220 * won't be valid. In cases like kexec, in which you install a new kernel, this
221 * means a random memory location will be kept being written. So before any
222 * kind of shutdown from our side, we unregister the clock by writing anything
223 * that does not have the 'enable' bit set in the msr
224 */
225 #ifdef CONFIG_KEXEC_CORE
kvm_crash_shutdown(struct pt_regs * regs)226 static void kvm_crash_shutdown(struct pt_regs *regs)
227 {
228 native_write_msr(msr_kvm_system_time, 0, 0);
229 kvm_disable_steal_time();
230 native_machine_crash_shutdown(regs);
231 }
232 #endif
233
kvm_shutdown(void)234 static void kvm_shutdown(void)
235 {
236 native_write_msr(msr_kvm_system_time, 0, 0);
237 kvm_disable_steal_time();
238 native_machine_shutdown();
239 }
240
kvmclock_init_mem(void)241 static void __init kvmclock_init_mem(void)
242 {
243 unsigned long ncpus;
244 unsigned int order;
245 struct page *p;
246 int r;
247
248 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
249 return;
250
251 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
252 order = get_order(ncpus * sizeof(*hvclock_mem));
253
254 p = alloc_pages(GFP_KERNEL, order);
255 if (!p) {
256 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
257 return;
258 }
259
260 hvclock_mem = page_address(p);
261
262 /*
263 * hvclock is shared between the guest and the hypervisor, must
264 * be mapped decrypted.
265 */
266 if (sev_active()) {
267 r = set_memory_decrypted((unsigned long) hvclock_mem,
268 1UL << order);
269 if (r) {
270 __free_pages(p, order);
271 hvclock_mem = NULL;
272 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
273 return;
274 }
275 }
276
277 memset(hvclock_mem, 0, PAGE_SIZE << order);
278 }
279
kvm_setup_vsyscall_timeinfo(void)280 static int __init kvm_setup_vsyscall_timeinfo(void)
281 {
282 #ifdef CONFIG_X86_64
283 u8 flags;
284
285 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall)
286 return 0;
287
288 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
289 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
290 return 0;
291
292 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
293 #endif
294
295 kvmclock_init_mem();
296
297 return 0;
298 }
299 early_initcall(kvm_setup_vsyscall_timeinfo);
300
kvmclock_setup_percpu(unsigned int cpu)301 static int kvmclock_setup_percpu(unsigned int cpu)
302 {
303 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
304
305 /*
306 * The per cpu area setup replicates CPU0 data to all cpu
307 * pointers. So carefully check. CPU0 has been set up in init
308 * already.
309 */
310 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
311 return 0;
312
313 /* Use the static page for the first CPUs, allocate otherwise */
314 if (cpu < HVC_BOOT_ARRAY_SIZE)
315 p = &hv_clock_boot[cpu];
316 else if (hvclock_mem)
317 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
318 else
319 return -ENOMEM;
320
321 per_cpu(hv_clock_per_cpu, cpu) = p;
322 return p ? 0 : -ENOMEM;
323 }
324
kvmclock_init(void)325 void __init kvmclock_init(void)
326 {
327 u8 flags;
328
329 if (!kvm_para_available() || !kvmclock)
330 return;
331
332 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
333 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
334 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
335 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
336 return;
337 }
338
339 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
340 kvmclock_setup_percpu, NULL) < 0) {
341 return;
342 }
343
344 pr_info("kvm-clock: Using msrs %x and %x",
345 msr_kvm_system_time, msr_kvm_wall_clock);
346
347 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
348 kvm_register_clock("primary cpu clock");
349 pvclock_set_pvti_cpu0_va(hv_clock_boot);
350
351 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
352 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
353
354 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
355 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
356
357 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
358 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
359 x86_platform.get_wallclock = kvm_get_wallclock;
360 x86_platform.set_wallclock = kvm_set_wallclock;
361 #ifdef CONFIG_X86_LOCAL_APIC
362 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
363 #endif
364 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
365 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
366 machine_ops.shutdown = kvm_shutdown;
367 #ifdef CONFIG_KEXEC_CORE
368 machine_ops.crash_shutdown = kvm_crash_shutdown;
369 #endif
370 kvm_get_preset_lpj();
371 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
372 pv_info.name = "KVM";
373 }
374
