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Linux/arch/x86/kernel/kvmclock.c

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

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