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.
6 #include <linux/clocksource.h>
7 #include <linux/kvm_para.h>
8 #include <asm/pvclock.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>
17 #include <linux/slab.h>
18 #include <linux/set_memory.h>
19 #include <linux/cc_platform.h>
21 #include <asm/hypervisor.h>
22 #include <asm/x86_init.h>
23 #include <asm/kvmclock.h>
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
;
31 static int __init
parse_no_kvmclock(char *arg
)
36 early_param("no-kvmclock", parse_no_kvmclock
);
38 static int __init
parse_no_kvmclock_vsyscall(char *arg
)
40 kvmclock_vsyscall
= 0;
43 early_param("no-kvmclock-vsyscall", parse_no_kvmclock_vsyscall
);
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))
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
);
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
61 static void kvm_get_wallclock(struct timespec64
*now
)
63 wrmsrl(msr_kvm_wall_clock
, slow_virt_to_phys(&wall_clock
));
65 pvclock_read_wallclock(&wall_clock
, this_cpu_pvti(), now
);
69 static int kvm_set_wallclock(const struct timespec64
*now
)
74 static u64
kvm_clock_read(void)
78 preempt_disable_notrace();
79 ret
= pvclock_clocksource_read_nowd(this_cpu_pvti());
80 preempt_enable_notrace();
84 static u64
kvm_clock_get_cycles(struct clocksource
*cs
)
86 return kvm_clock_read();
89 static noinstr u64
kvm_sched_clock_read(void)
91 return pvclock_clocksource_read_nowd(this_cpu_pvti()) - kvm_sched_clock_offset
;
94 static inline void kvm_sched_clock_init(bool stable
)
97 clear_sched_clock_stable();
98 kvm_sched_clock_offset
= kvm_clock_read();
99 paravirt_set_sched_clock(kvm_sched_clock_read
);
101 pr_info("kvm-clock: using sched offset of %llu cycles",
102 kvm_sched_clock_offset
);
104 BUILD_BUG_ON(sizeof(kvm_sched_clock_offset
) >
105 sizeof(((struct pvclock_vcpu_time_info
*)NULL
)->system_time
));
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
117 static unsigned long kvm_get_tsc_khz(void)
119 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ
);
120 return pvclock_tsc_khz(this_cpu_pvti());
123 static void __init
kvm_get_preset_lpj(void)
128 khz
= kvm_get_tsc_khz();
130 lpj
= ((u64
)khz
* 1000);
135 bool kvm_check_and_clear_guest_paused(void)
137 struct pvclock_vsyscall_time_info
*src
= this_cpu_hvclock();
143 if ((src
->pvti
.flags
& PVCLOCK_GUEST_STOPPED
) != 0) {
144 src
->pvti
.flags
&= ~PVCLOCK_GUEST_STOPPED
;
145 pvclock_touch_watchdogs();
151 static int kvm_cs_enable(struct clocksource
*cs
)
153 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK
);
157 static struct clocksource kvm_clock
= {
159 .read
= kvm_clock_get_cycles
,
161 .mask
= CLOCKSOURCE_MASK(64),
162 .flags
= CLOCK_SOURCE_IS_CONTINUOUS
,
163 .id
= CSID_X86_KVM_CLK
,
164 .enable
= kvm_cs_enable
,
167 static void kvm_register_clock(char *txt
)
169 struct pvclock_vsyscall_time_info
*src
= this_cpu_hvclock();
175 pa
= slow_virt_to_phys(&src
->pvti
) | 0x01ULL
;
176 wrmsrl(msr_kvm_system_time
, pa
);
177 pr_debug("kvm-clock: cpu %d, msr %llx, %s", smp_processor_id(), pa
, txt
);
180 static void kvm_save_sched_clock_state(void)
184 static void kvm_restore_sched_clock_state(void)
186 kvm_register_clock("primary cpu clock, resume");
189 #ifdef CONFIG_X86_LOCAL_APIC
190 static void kvm_setup_secondary_clock(void)
192 kvm_register_clock("secondary cpu clock");
196 void kvmclock_disable(void)
198 if (msr_kvm_system_time
)
199 native_write_msr(msr_kvm_system_time
, 0, 0);
202 static void __init
kvmclock_init_mem(void)
209 if (HVC_BOOT_ARRAY_SIZE
>= num_possible_cpus())
212 ncpus
= num_possible_cpus() - HVC_BOOT_ARRAY_SIZE
;
213 order
= get_order(ncpus
* sizeof(*hvclock_mem
));
215 p
= alloc_pages(GFP_KERNEL
, order
);
217 pr_warn("%s: failed to alloc %d pages", __func__
, (1U << order
));
221 hvclock_mem
= page_address(p
);
224 * hvclock is shared between the guest and the hypervisor, must
225 * be mapped decrypted.
227 if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT
)) {
228 r
= set_memory_decrypted((unsigned long) hvclock_mem
,
231 __free_pages(p
, order
);
233 pr_warn("kvmclock: set_memory_decrypted() failed. Disabling\n");
238 memset(hvclock_mem
, 0, PAGE_SIZE
<< order
);
241 static int __init
kvm_setup_vsyscall_timeinfo(void)
243 if (!kvm_para_available() || !kvmclock
|| nopv
)
249 if (per_cpu(hv_clock_per_cpu
, 0) && kvmclock_vsyscall
) {
252 flags
= pvclock_read_flags(&hv_clock_boot
[0].pvti
);
253 if (!(flags
& PVCLOCK_TSC_STABLE_BIT
))
256 kvm_clock
.vdso_clock_mode
= VDSO_CLOCKMODE_PVCLOCK
;
262 early_initcall(kvm_setup_vsyscall_timeinfo
);
264 static int kvmclock_setup_percpu(unsigned int cpu
)
266 struct pvclock_vsyscall_time_info
*p
= per_cpu(hv_clock_per_cpu
, cpu
);
269 * The per cpu area setup replicates CPU0 data to all cpu
270 * pointers. So carefully check. CPU0 has been set up in init
273 if (!cpu
|| (p
&& p
!= per_cpu(hv_clock_per_cpu
, 0)))
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
;
284 per_cpu(hv_clock_per_cpu
, cpu
) = p
;
285 return p
? 0 : -ENOMEM
;
288 void __init
kvmclock_init(void)
292 if (!kvm_para_available() || !kvmclock
)
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
;
305 if (cpuhp_setup_state(CPUHP_BP_PREPARE_DYN
, "kvmclock:setup_percpu",
306 kvmclock_setup_percpu
, NULL
) < 0) {
310 pr_info("kvm-clock: Using msrs %x and %x",
311 msr_kvm_system_time
, msr_kvm_wall_clock
);
313 this_cpu_write(hv_clock_per_cpu
, &hv_clock_boot
[0]);
314 kvm_register_clock("primary cpu clock");
315 pvclock_set_pvti_cpu0_va(hv_clock_boot
);
317 if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT
))
318 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
);
320 flags
= pvclock_read_flags(&hv_clock_boot
[0].pvti
);
321 kvm_sched_clock_init(flags
& PVCLOCK_TSC_STABLE_BIT
);
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
;
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();
335 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
336 * with P/T states and does not stop in deep C-states.
338 * Invariant TSC exposed by host means kvmclock is not necessary:
339 * can use TSC as clocksource.
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;
347 clocksource_register_hz(&kvm_clock
, NSEC_PER_SEC
);
348 pv_info
.name
= "KVM";