x86: KVM guest: kvm_get_tsc_khz: return khz, not lpj
[linux-2.6.git] / 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/arch_hooks.h>
23 #include <asm/msr.h>
24 #include <asm/apic.h>
25 #include <linux/percpu.h>
26 #include <asm/reboot.h>
27
28 #define KVM_SCALE 22
29
30 static int kvmclock = 1;
31
32 static int parse_no_kvmclock(char *arg)
33 {
34         kvmclock = 0;
35         return 0;
36 }
37 early_param("no-kvmclock", parse_no_kvmclock);
38
39 /* The hypervisor will put information about time periodically here */
40 static DEFINE_PER_CPU_SHARED_ALIGNED(struct pvclock_vcpu_time_info, hv_clock);
41 static struct pvclock_wall_clock wall_clock;
42
43 /*
44  * The wallclock is the time of day when we booted. Since then, some time may
45  * have elapsed since the hypervisor wrote the data. So we try to account for
46  * that with system time
47  */
48 static unsigned long kvm_get_wallclock(void)
49 {
50         struct pvclock_vcpu_time_info *vcpu_time;
51         struct timespec ts;
52         int low, high;
53
54         low = (int)__pa(&wall_clock);
55         high = ((u64)__pa(&wall_clock) >> 32);
56         native_write_msr(MSR_KVM_WALL_CLOCK, low, high);
57
58         vcpu_time = &get_cpu_var(hv_clock);
59         pvclock_read_wallclock(&wall_clock, vcpu_time, &ts);
60         put_cpu_var(hv_clock);
61
62         return ts.tv_sec;
63 }
64
65 static int kvm_set_wallclock(unsigned long now)
66 {
67         return -1;
68 }
69
70 static cycle_t kvm_clock_read(void)
71 {
72         struct pvclock_vcpu_time_info *src;
73         cycle_t ret;
74
75         src = &get_cpu_var(hv_clock);
76         ret = pvclock_clocksource_read(src);
77         put_cpu_var(hv_clock);
78         return ret;
79 }
80
81 /*
82  * If we don't do that, there is the possibility that the guest
83  * will calibrate under heavy load - thus, getting a lower lpj -
84  * and execute the delays themselves without load. This is wrong,
85  * because no delay loop can finish beforehand.
86  * Any heuristics is subject to fail, because ultimately, a large
87  * poll of guests can be running and trouble each other. So we preset
88  * lpj here
89  */
90 static unsigned long kvm_get_tsc_khz(void)
91 {
92         struct pvclock_vcpu_time_info *src;
93         src = &per_cpu(hv_clock, 0);
94         return pvclock_tsc_khz(src);
95 }
96
97 static void kvm_get_preset_lpj(void)
98 {
99         unsigned long khz;
100         u64 lpj;
101
102         khz = kvm_get_tsc_khz();
103
104         lpj = ((u64)khz * 1000);
105         do_div(lpj, HZ);
106         preset_lpj = lpj;
107 }
108
109 static struct clocksource kvm_clock = {
110         .name = "kvm-clock",
111         .read = kvm_clock_read,
112         .rating = 400,
113         .mask = CLOCKSOURCE_MASK(64),
114         .mult = 1 << KVM_SCALE,
115         .shift = KVM_SCALE,
116         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
117 };
118
119 static int kvm_register_clock(char *txt)
120 {
121         int cpu = smp_processor_id();
122         int low, high;
123         low = (int)__pa(&per_cpu(hv_clock, cpu)) | 1;
124         high = ((u64)__pa(&per_cpu(hv_clock, cpu)) >> 32);
125         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
126                cpu, high, low, txt);
127         return native_write_msr_safe(MSR_KVM_SYSTEM_TIME, low, high);
128 }
129
130 #ifdef CONFIG_X86_LOCAL_APIC
131 static void __cpuinit kvm_setup_secondary_clock(void)
132 {
133         /*
134          * Now that the first cpu already had this clocksource initialized,
135          * we shouldn't fail.
136          */
137         WARN_ON(kvm_register_clock("secondary cpu clock"));
138         /* ok, done with our trickery, call native */
139         setup_secondary_APIC_clock();
140 }
141 #endif
142
143 #ifdef CONFIG_SMP
144 static void __init kvm_smp_prepare_boot_cpu(void)
145 {
146         WARN_ON(kvm_register_clock("primary cpu clock"));
147         native_smp_prepare_boot_cpu();
148 }
149 #endif
150
151 /*
152  * After the clock is registered, the host will keep writing to the
153  * registered memory location. If the guest happens to shutdown, this memory
154  * won't be valid. In cases like kexec, in which you install a new kernel, this
155  * means a random memory location will be kept being written. So before any
156  * kind of shutdown from our side, we unregister the clock by writting anything
157  * that does not have the 'enable' bit set in the msr
158  */
159 #ifdef CONFIG_KEXEC
160 static void kvm_crash_shutdown(struct pt_regs *regs)
161 {
162         native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
163         native_machine_crash_shutdown(regs);
164 }
165 #endif
166
167 static void kvm_shutdown(void)
168 {
169         native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0);
170         native_machine_shutdown();
171 }
172
173 void __init kvmclock_init(void)
174 {
175         if (!kvm_para_available())
176                 return;
177
178         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)) {
179                 if (kvm_register_clock("boot clock"))
180                         return;
181                 pv_time_ops.get_wallclock = kvm_get_wallclock;
182                 pv_time_ops.set_wallclock = kvm_set_wallclock;
183                 pv_time_ops.sched_clock = kvm_clock_read;
184                 pv_time_ops.get_tsc_khz = kvm_get_tsc_khz;
185 #ifdef CONFIG_X86_LOCAL_APIC
186                 pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock;
187 #endif
188 #ifdef CONFIG_SMP
189                 smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
190 #endif
191                 machine_ops.shutdown  = kvm_shutdown;
192 #ifdef CONFIG_KEXEC
193                 machine_ops.crash_shutdown  = kvm_crash_shutdown;
194 #endif
195                 kvm_get_preset_lpj();
196                 clocksource_register(&kvm_clock);
197                 pv_info.paravirt_enabled = 1;
198                 pv_info.name = "KVM";
199         }
200 }