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/memblock.h>
27
28#include <asm/x86_init.h>
29#include <asm/reboot.h>
30
31static int kvmclock = 1;
32static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
33static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
34
35static int parse_no_kvmclock(char *arg)
36{
37	kvmclock = 0;
38	return 0;
39}
40early_param("no-kvmclock", parse_no_kvmclock);
41
42/* The hypervisor will put information about time periodically here */
43static struct pvclock_vsyscall_time_info *hv_clock;
44static struct pvclock_wall_clock wall_clock;
45
46/*
47 * The wallclock is the time of day when we booted. Since then, some time may
48 * have elapsed since the hypervisor wrote the data. So we try to account for
49 * that with system time
50 */
51static void kvm_get_wallclock(struct timespec *now)
52{
53	struct pvclock_vcpu_time_info *vcpu_time;
54	int low, high;
55	int cpu;
56
57	low = (int)__pa_symbol(&wall_clock);
58	high = ((u64)__pa_symbol(&wall_clock) >> 32);
59
60	native_write_msr(msr_kvm_wall_clock, low, high);
61
62	preempt_disable();
63	cpu = smp_processor_id();
64
65	vcpu_time = &hv_clock[cpu].pvti;
66	pvclock_read_wallclock(&wall_clock, vcpu_time, now);
67
68	preempt_enable();
69}
70
71static int kvm_set_wallclock(const struct timespec *now)
72{
73	return -1;
74}
75
76static cycle_t kvm_clock_read(void)
77{
78	struct pvclock_vcpu_time_info *src;
79	cycle_t ret;
80	int cpu;
81
82	preempt_disable_notrace();
83	cpu = smp_processor_id();
84	src = &hv_clock[cpu].pvti;
85	ret = pvclock_clocksource_read(src);
86	preempt_enable_notrace();
87	return ret;
88}
89
90static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
91{
92	return kvm_clock_read();
93}
94
95/*
96 * If we don't do that, there is the possibility that the guest
97 * will calibrate under heavy load - thus, getting a lower lpj -
98 * and execute the delays themselves without load. This is wrong,
99 * because no delay loop can finish beforehand.
100 * Any heuristics is subject to fail, because ultimately, a large
101 * poll of guests can be running and trouble each other. So we preset
102 * lpj here
103 */
104static unsigned long kvm_get_tsc_khz(void)
105{
106	struct pvclock_vcpu_time_info *src;
107	int cpu;
108	unsigned long tsc_khz;
109
110	preempt_disable();
111	cpu = smp_processor_id();
112	src = &hv_clock[cpu].pvti;
113	tsc_khz = pvclock_tsc_khz(src);
114	preempt_enable();
115	return tsc_khz;
116}
117
118static void kvm_get_preset_lpj(void)
119{
120	unsigned long khz;
121	u64 lpj;
122
123	khz = kvm_get_tsc_khz();
124
125	lpj = ((u64)khz * 1000);
126	do_div(lpj, HZ);
127	preset_lpj = lpj;
128}
129
130bool kvm_check_and_clear_guest_paused(void)
131{
132	bool ret = false;
133	struct pvclock_vcpu_time_info *src;
134	int cpu = smp_processor_id();
135
136	if (!hv_clock)
137		return ret;
138
139	src = &hv_clock[cpu].pvti;
140	if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
141		src->flags &= ~PVCLOCK_GUEST_STOPPED;
142		pvclock_touch_watchdogs();
143		ret = true;
144	}
145
146	return ret;
147}
148
149static struct clocksource kvm_clock = {
150	.name = "kvm-clock",
151	.read = kvm_clock_get_cycles,
152	.rating = 400,
153	.mask = CLOCKSOURCE_MASK(64),
154	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
155};
156
157int kvm_register_clock(char *txt)
158{
159	int cpu = smp_processor_id();
160	int low, high, ret;
161	struct pvclock_vcpu_time_info *src;
162
163	if (!hv_clock)
164		return 0;
165
166	src = &hv_clock[cpu].pvti;
167	low = (int)slow_virt_to_phys(src) | 1;
168	high = ((u64)slow_virt_to_phys(src) >> 32);
169	ret = native_write_msr_safe(msr_kvm_system_time, low, high);
170	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
171	       cpu, high, low, txt);
172
173	return ret;
174}
175
176static void kvm_save_sched_clock_state(void)
177{
178}
179
180static void kvm_restore_sched_clock_state(void)
181{
182	kvm_register_clock("primary cpu clock, resume");
183}
184
185#ifdef CONFIG_X86_LOCAL_APIC
186static void kvm_setup_secondary_clock(void)
187{
188	/*
189	 * Now that the first cpu already had this clocksource initialized,
190	 * we shouldn't fail.
191	 */
192	WARN_ON(kvm_register_clock("secondary cpu clock"));
193}
194#endif
195
196/*
197 * After the clock is registered, the host will keep writing to the
198 * registered memory location. If the guest happens to shutdown, this memory
199 * won't be valid. In cases like kexec, in which you install a new kernel, this
200 * means a random memory location will be kept being written. So before any
201 * kind of shutdown from our side, we unregister the clock by writting anything
202 * that does not have the 'enable' bit set in the msr
203 */
204#ifdef CONFIG_KEXEC
205static void kvm_crash_shutdown(struct pt_regs *regs)
206{
207	native_write_msr(msr_kvm_system_time, 0, 0);
208	kvm_disable_steal_time();
209	native_machine_crash_shutdown(regs);
210}
211#endif
212
213static void kvm_shutdown(void)
214{
215	native_write_msr(msr_kvm_system_time, 0, 0);
216	kvm_disable_steal_time();
217	native_machine_shutdown();
218}
219
220void __init kvmclock_init(void)
221{
222	unsigned long mem;
223	int size;
224
225	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
226
227	if (!kvm_para_available())
228		return;
229
230	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
231		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
232		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
233	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
234		return;
235
236	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
237		msr_kvm_system_time, msr_kvm_wall_clock);
238
239	mem = memblock_alloc(size, PAGE_SIZE);
240	if (!mem)
241		return;
242	hv_clock = __va(mem);
243	memset(hv_clock, 0, size);
244
245	if (kvm_register_clock("primary cpu clock")) {
246		hv_clock = NULL;
247		memblock_free(mem, size);
248		return;
249	}
250	pv_time_ops.sched_clock = kvm_clock_read;
251	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
252	x86_platform.get_wallclock = kvm_get_wallclock;
253	x86_platform.set_wallclock = kvm_set_wallclock;
254#ifdef CONFIG_X86_LOCAL_APIC
255	x86_cpuinit.early_percpu_clock_init =
256		kvm_setup_secondary_clock;
257#endif
258	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
259	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
260	machine_ops.shutdown  = kvm_shutdown;
261#ifdef CONFIG_KEXEC
262	machine_ops.crash_shutdown  = kvm_crash_shutdown;
263#endif
264	kvm_get_preset_lpj();
265	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
266	pv_info.paravirt_enabled = 1;
267	pv_info.name = "KVM";
268
269	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
270		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
271}
272
273int __init kvm_setup_vsyscall_timeinfo(void)
274{
275#ifdef CONFIG_X86_64
276	int cpu;
277	int ret;
278	u8 flags;
279	struct pvclock_vcpu_time_info *vcpu_time;
280	unsigned int size;
281
282	if (!hv_clock)
283		return 0;
284
285	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
286
287	preempt_disable();
288	cpu = smp_processor_id();
289
290	vcpu_time = &hv_clock[cpu].pvti;
291	flags = pvclock_read_flags(vcpu_time);
292
293	if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
294		preempt_enable();
295		return 1;
296	}
297
298	if ((ret = pvclock_init_vsyscall(hv_clock, size))) {
299		preempt_enable();
300		return ret;
301	}
302
303	preempt_enable();
304
305	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
306#endif
307	return 0;
308}
309