/arch/x86/kernel/kvmclock.c

  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
 26#include <asm/x86_init.h>
 27#include <asm/reboot.h>
 28
 29#define KVM_SCALE 22
 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 DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_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 unsigned long kvm_get_wallclock(void)
 52{
 53	struct pvclock_vcpu_time_info *vcpu_time;
 54	struct timespec ts;
 55	int low, high;
 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	vcpu_time = &get_cpu_var(hv_clock);
 63	pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
 64	put_cpu_var(hv_clock);
 65
 66	return ts.tv_sec;
 67}
 68
 69static int kvm_set_wallclock(unsigned long now)
 70{
 71	return -1;
 72}
 73
 74static cycle_t kvm_clock_read(void)
 75{
 76	struct pvclock_vcpu_time_info *src;
 77	cycle_t ret;
 78
 79	src = &get_cpu_var(hv_clock);
 80	ret = pvclock_clocksource_read(src);
 81	put_cpu_var(hv_clock);
 82	return ret;
 83}
 84
 85static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
 86{
 87	return kvm_clock_read();
 88}
 89
 90/*
 91 * If we don't do that, there is the possibility that the guest
 92 * will calibrate under heavy load - thus, getting a lower lpj -
 93 * and execute the delays themselves without load. This is wrong,
 94 * because no delay loop can finish beforehand.
 95 * Any heuristics is subject to fail, because ultimately, a large
 96 * poll of guests can be running and trouble each other. So we preset
 97 * lpj here
 98 */
 99static unsigned long kvm_get_tsc_khz(void)
100{
101	struct pvclock_vcpu_time_info *src;
102	src = &per_cpu(hv_clock, 0);
103	return pvclock_tsc_khz(src);
104}
105
106static void kvm_get_preset_lpj(void)
107{
108	unsigned long khz;
109	u64 lpj;
110
111	khz = kvm_get_tsc_khz();
112
113	lpj = ((u64)khz * 1000);
114	do_div(lpj, HZ);
115	preset_lpj = lpj;
116}
117
118static struct clocksource kvm_clock = {
119	.name = "kvm-clock",
120	.read = kvm_clock_get_cycles,
121	.rating = 400,
122	.mask = CLOCKSOURCE_MASK(64),
123	.mult = 1 << KVM_SCALE,
124	.shift = KVM_SCALE,
125	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
126};
127
128static int kvm_register_clock(char *txt)
129{
130	int cpu = smp_processor_id();
131	int low, high;
132	low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
133	high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
134	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
135	       cpu, high, low, txt);
136
137	return native_write_msr_safe(msr_kvm_system_time, low, high);
138}
139
140#ifdef CONFIG_X86_LOCAL_APIC
141static void __cpuinit kvm_setup_secondary_clock(void)
142{
143	/*
144	 * Now that the first cpu already had this clocksource initialized,
145	 * we shouldn't fail.
146	 */
147	WARN_ON(kvm_register_clock("secondary cpu clock"));
148	/* ok, done with our trickery, call native */
149	setup_secondary_APIC_clock();
150}
151#endif
152
153#ifdef CONFIG_SMP
154static void __init kvm_smp_prepare_boot_cpu(void)
155{
156	WARN_ON(kvm_register_clock("primary cpu clock"));
157	native_smp_prepare_boot_cpu();
158}
159#endif
160
161/*
162 * After the clock is registered, the host will keep writing to the
163 * registered memory location. If the guest happens to shutdown, this memory
164 * won't be valid. In cases like kexec, in which you install a new kernel, this
165 * means a random memory location will be kept being written. So before any
166 * kind of shutdown from our side, we unregister the clock by writting anything
167 * that does not have the 'enable' bit set in the msr
168 */
169#ifdef CONFIG_KEXEC
170static void kvm_crash_shutdown(struct pt_regs *regs)
171{
172	native_write_msr(msr_kvm_system_time, 0, 0);
173	native_machine_crash_shutdown(regs);
174}
175#endif
176
177static void kvm_shutdown(void)
178{
179	native_write_msr(msr_kvm_system_time, 0, 0);
180	native_machine_shutdown();
181}
182
183void __init kvmclock_init(void)
184{
185	if (!kvm_para_available())
186		return;
187
188	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
189		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
190		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
191	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
192		return;
193
194	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
195		msr_kvm_system_time, msr_kvm_wall_clock);
196
197	if (kvm_register_clock("boot clock"))
198		return;
199	pv_time_ops.sched_clock = kvm_clock_read;
200	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
201	x86_platform.get_wallclock = kvm_get_wallclock;
202	x86_platform.set_wallclock = kvm_set_wallclock;
203#ifdef CONFIG_X86_LOCAL_APIC
204	x86_cpuinit.setup_percpu_clockev =
205		kvm_setup_secondary_clock;
206#endif
207#ifdef CONFIG_SMP
208	smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
209#endif
210	machine_ops.shutdown  = kvm_shutdown;
211#ifdef CONFIG_KEXEC
212	machine_ops.crash_shutdown  = kvm_crash_shutdown;
213#endif
214	kvm_get_preset_lpj();
215	clocksource_register(&kvm_clock);
216	pv_info.paravirt_enabled = 1;
217	pv_info.name = "KVM";
218
219	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
220		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
221}