1 /* KVM paravirtual clock driver. A clocksource implementation
2 Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
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.
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.
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
19 #include <linux/clocksource.h>
20 #include <linux/kvm_para.h>
21 #include <asm/pvclock.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>
30 #include <linux/slab.h>
31 #include <linux/set_memory.h>
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>
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;
45 static int __init parse_no_kvmclock(char *arg)
50 early_param("no-kvmclock", parse_no_kvmclock);
52 static int __init parse_no_kvmclock_vsyscall(char *arg)
54 kvmclock_vsyscall = 0;
57 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall);
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))
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 struct pvclock_vsyscall_time_info *hvclock_mem;
68 DEFINE_PER_CPU(struct pvclock_vsyscall_time_info *, hv_clock_per_cpu);
69 EXPORT_PER_CPU_SYMBOL_GPL(hv_clock_per_cpu);
72 * The wallclock is the time of day when we booted. Since then, some time may
73 * have elapsed since the hypervisor wrote the data. So we try to account for
74 * that with system time
76 static void kvm_get_wallclock(struct timespec64 *now)
78 wrmsrl(msr_kvm_wall_clock, slow_virt_to_phys(&wall_clock));
80 pvclock_read_wallclock(&wall_clock, this_cpu_pvti(), now);
84 static int kvm_set_wallclock(const struct timespec64 *now)
89 static u64 kvm_clock_read(void)
93 preempt_disable_notrace();
94 ret = pvclock_clocksource_read(this_cpu_pvti());
95 preempt_enable_notrace();
99 static u64 kvm_clock_get_cycles(struct clocksource *cs)
101 return kvm_clock_read();
104 static u64 kvm_sched_clock_read(void)
106 return kvm_clock_read() - kvm_sched_clock_offset;
109 static inline void kvm_sched_clock_init(bool stable)
112 clear_sched_clock_stable();
113 kvm_sched_clock_offset = kvm_clock_read();
114 pv_time_ops.sched_clock = kvm_sched_clock_read;
116 pr_info("kvm-clock: using sched offset of %llu cycles",
117 kvm_sched_clock_offset);
119 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
120 sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
124 * If we don't do that, there is the possibility that the guest
125 * will calibrate under heavy load - thus, getting a lower lpj -
126 * and execute the delays themselves without load. This is wrong,
127 * because no delay loop can finish beforehand.
128 * Any heuristics is subject to fail, because ultimately, a large
129 * poll of guests can be running and trouble each other. So we preset
132 static unsigned long kvm_get_tsc_khz(void)
134 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
135 return pvclock_tsc_khz(this_cpu_pvti());
138 static void __init kvm_get_preset_lpj(void)
143 khz = kvm_get_tsc_khz();
145 lpj = ((u64)khz * 1000);
150 bool kvm_check_and_clear_guest_paused(void)
152 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
158 if ((src->pvti.flags & PVCLOCK_GUEST_STOPPED) != 0) {
159 src->pvti.flags &= ~PVCLOCK_GUEST_STOPPED;
160 pvclock_touch_watchdogs();
166 struct clocksource kvm_clock = {
168 .read = kvm_clock_get_cycles,
170 .mask = CLOCKSOURCE_MASK(64),
171 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
173 EXPORT_SYMBOL_GPL(kvm_clock);
175 static void kvm_register_clock(char *txt)
177 struct pvclock_vsyscall_time_info *src = this_cpu_hvclock();
183 pa = slow_virt_to_phys(&src->pvti) | 0x01ULL;
184 wrmsrl(msr_kvm_system_time, pa);
185 pr_info("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa, txt);
188 static void kvm_save_sched_clock_state(void)
192 static void kvm_restore_sched_clock_state(void)
194 kvm_register_clock("primary cpu clock, resume");
197 #ifdef CONFIG_X86_LOCAL_APIC
198 static void kvm_setup_secondary_clock(void)
200 kvm_register_clock("secondary cpu clock");
205 * After the clock is registered, the host will keep writing to the
206 * registered memory location. If the guest happens to shutdown, this memory
207 * won't be valid. In cases like kexec, in which you install a new kernel, this
208 * means a random memory location will be kept being written. So before any
209 * kind of shutdown from our side, we unregister the clock by writing anything
210 * that does not have the 'enable' bit set in the msr
212 #ifdef CONFIG_KEXEC_CORE
213 static void kvm_crash_shutdown(struct pt_regs *regs)
215 native_write_msr(msr_kvm_system_time, 0, 0);
216 kvm_disable_steal_time();
217 native_machine_crash_shutdown(regs);
221 static void kvm_shutdown(void)
223 native_write_msr(msr_kvm_system_time, 0, 0);
224 kvm_disable_steal_time();
225 native_machine_shutdown();
228 static void __init kvmclock_init_mem(void)
235 if (HVC_BOOT_ARRAY_SIZE >= num_possible_cpus())
238 ncpus = num_possible_cpus() - HVC_BOOT_ARRAY_SIZE;
239 order = get_order(ncpus * sizeof(*hvclock_mem));
241 p = alloc_pages(GFP_KERNEL, order);
243 pr_warn("%s: failed to alloc %d pages", __func__, (1U << order));
247 hvclock_mem = page_address(p);
250 * hvclock is shared between the guest and the hypervisor, must
251 * be mapped decrypted.
254 r = set_memory_decrypted((unsigned long) hvclock_mem,
257 __free_pages(p, order);
259 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
264 memset(hvclock_mem, 0, PAGE_SIZE << order);
267 static int __init kvm_setup_vsyscall_timeinfo(void)
272 if (!per_cpu(hv_clock_per_cpu, 0) || !kvmclock_vsyscall)
275 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
276 if (!(flags & PVCLOCK_TSC_STABLE_BIT))
279 kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
286 early_initcall(kvm_setup_vsyscall_timeinfo);
288 static int kvmclock_setup_percpu(unsigned int cpu)
290 struct pvclock_vsyscall_time_info *p = per_cpu(hv_clock_per_cpu, cpu);
293 * The per cpu area setup replicates CPU0 data to all cpu
294 * pointers. So carefully check. CPU0 has been set up in init
297 if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
300 /* Use the static page for the first CPUs, allocate otherwise */
301 if (cpu < HVC_BOOT_ARRAY_SIZE)
302 p = &hv_clock_boot[cpu];
303 else if (hvclock_mem)
304 p = hvclock_mem + cpu - HVC_BOOT_ARRAY_SIZE;
308 per_cpu(hv_clock_per_cpu, cpu) = p;
309 return p ? 0 : -ENOMEM;
312 void __init kvmclock_init(void)
316 if (!kvm_para_available() || !kvmclock)
319 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
320 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
321 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
322 } else if (!kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
326 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "kvmclock:setup_percpu",
327 kvmclock_setup_percpu, NULL) < 0) {
331 pr_info("kvm-clock: Using msrs %x and %x",
332 msr_kvm_system_time, msr_kvm_wall_clock);
334 this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]);
335 kvm_register_clock("primary cpu clock");
336 pvclock_set_pvti_cpu0_va(hv_clock_boot);
338 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
339 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
341 flags = pvclock_read_flags(&hv_clock_boot[0].pvti);
342 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
344 x86_platform.calibrate_tsc = kvm_get_tsc_khz;
345 x86_platform.calibrate_cpu = kvm_get_tsc_khz;
346 x86_platform.get_wallclock = kvm_get_wallclock;
347 x86_platform.set_wallclock = kvm_set_wallclock;
348 #ifdef CONFIG_X86_LOCAL_APIC
349 x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
351 x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
352 x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
353 machine_ops.shutdown = kvm_shutdown;
354 #ifdef CONFIG_KEXEC_CORE
355 machine_ops.crash_shutdown = kvm_crash_shutdown;
357 kvm_get_preset_lpj();
358 clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
359 pv_info.name = "KVM";