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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 #include <linux/sched.h>
 28 
 29 #include <asm/x86_init.h>
 30 #include <asm/reboot.h>
 31 
 32 static int kvmclock = 1;
 33 static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
 34 static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
 35 static cycle_t kvm_sched_clock_offset;
 36 
 37 static int parse_no_kvmclock(char *arg)
 38 {
 39         kvmclock = 0;
 40         return 0;
 41 }
 42 early_param("no-kvmclock", parse_no_kvmclock);
 43 
 44 /* The hypervisor will put information about time periodically here */
 45 static struct pvclock_vsyscall_time_info *hv_clock;
 46 static struct pvclock_wall_clock wall_clock;
 47 
 48 struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
 49 {
 50         return hv_clock;
 51 }
 52 
 53 /*
 54  * The wallclock is the time of day when we booted. Since then, some time may
 55  * have elapsed since the hypervisor wrote the data. So we try to account for
 56  * that with system time
 57  */
 58 static void kvm_get_wallclock(struct timespec *now)
 59 {
 60         struct pvclock_vcpu_time_info *vcpu_time;
 61         int low, high;
 62         int cpu;
 63 
 64         low = (int)__pa_symbol(&wall_clock);
 65         high = ((u64)__pa_symbol(&wall_clock) >> 32);
 66 
 67         native_write_msr(msr_kvm_wall_clock, low, high);
 68 
 69         cpu = get_cpu();
 70 
 71         vcpu_time = &hv_clock[cpu].pvti;
 72         pvclock_read_wallclock(&wall_clock, vcpu_time, now);
 73 
 74         put_cpu();
 75 }
 76 
 77 static int kvm_set_wallclock(const struct timespec *now)
 78 {
 79         return -1;
 80 }
 81 
 82 static cycle_t kvm_clock_read(void)
 83 {
 84         struct pvclock_vcpu_time_info *src;
 85         cycle_t ret;
 86         int cpu;
 87 
 88         preempt_disable_notrace();
 89         cpu = smp_processor_id();
 90         src = &hv_clock[cpu].pvti;
 91         ret = pvclock_clocksource_read(src);
 92         preempt_enable_notrace();
 93         return ret;
 94 }
 95 
 96 static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
 97 {
 98         return kvm_clock_read();
 99 }
100 
101 static cycle_t kvm_sched_clock_read(void)
102 {
103         return kvm_clock_read() - kvm_sched_clock_offset;
104 }
105 
106 static inline void kvm_sched_clock_init(bool stable)
107 {
108         if (!stable) {
109                 pv_time_ops.sched_clock = kvm_clock_read;
110                 return;
111         }
112 
113         kvm_sched_clock_offset = kvm_clock_read();
114         pv_time_ops.sched_clock = kvm_sched_clock_read;
115         set_sched_clock_stable();
116 
117         printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
118                         kvm_sched_clock_offset);
119 
120         BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
121                  sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
122 }
123 
124 /*
125  * If we don't do that, there is the possibility that the guest
126  * will calibrate under heavy load - thus, getting a lower lpj -
127  * and execute the delays themselves without load. This is wrong,
128  * because no delay loop can finish beforehand.
129  * Any heuristics is subject to fail, because ultimately, a large
130  * poll of guests can be running and trouble each other. So we preset
131  * lpj here
132  */
133 static unsigned long kvm_get_tsc_khz(void)
134 {
135         struct pvclock_vcpu_time_info *src;
136         int cpu;
137         unsigned long tsc_khz;
138 
139         cpu = get_cpu();
140         src = &hv_clock[cpu].pvti;
141         tsc_khz = pvclock_tsc_khz(src);
142         put_cpu();
143         return tsc_khz;
144 }
145 
146 static void kvm_get_preset_lpj(void)
147 {
148         unsigned long khz;
149         u64 lpj;
150 
151         khz = kvm_get_tsc_khz();
152 
153         lpj = ((u64)khz * 1000);
154         do_div(lpj, HZ);
155         preset_lpj = lpj;
156 }
157 
158 bool kvm_check_and_clear_guest_paused(void)
159 {
160         bool ret = false;
161         struct pvclock_vcpu_time_info *src;
162         int cpu = smp_processor_id();
163 
164         if (!hv_clock)
165                 return ret;
166 
167         src = &hv_clock[cpu].pvti;
168         if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
169                 src->flags &= ~PVCLOCK_GUEST_STOPPED;
170                 pvclock_touch_watchdogs();
171                 ret = true;
172         }
173 
174         return ret;
175 }
176 
177 static struct clocksource kvm_clock = {
178         .name = "kvm-clock",
179         .read = kvm_clock_get_cycles,
180         .rating = 400,
181         .mask = CLOCKSOURCE_MASK(64),
182         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
183 };
184 
185 int kvm_register_clock(char *txt)
186 {
187         int cpu = smp_processor_id();
188         int low, high, ret;
189         struct pvclock_vcpu_time_info *src;
190 
191         if (!hv_clock)
192                 return 0;
193 
194         src = &hv_clock[cpu].pvti;
195         low = (int)slow_virt_to_phys(src) | 1;
196         high = ((u64)slow_virt_to_phys(src) >> 32);
197         ret = native_write_msr_safe(msr_kvm_system_time, low, high);
198         printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
199                cpu, high, low, txt);
200 
201         return ret;
202 }
203 
204 static void kvm_save_sched_clock_state(void)
205 {
206 }
207 
208 static void kvm_restore_sched_clock_state(void)
209 {
210         kvm_register_clock("primary cpu clock, resume");
211 }
212 
213 #ifdef CONFIG_X86_LOCAL_APIC
214 static void kvm_setup_secondary_clock(void)
215 {
216         /*
217          * Now that the first cpu already had this clocksource initialized,
218          * we shouldn't fail.
219          */
220         WARN_ON(kvm_register_clock("secondary cpu clock"));
221 }
222 #endif
223 
224 /*
225  * After the clock is registered, the host will keep writing to the
226  * registered memory location. If the guest happens to shutdown, this memory
227  * won't be valid. In cases like kexec, in which you install a new kernel, this
228  * means a random memory location will be kept being written. So before any
229  * kind of shutdown from our side, we unregister the clock by writing anything
230  * that does not have the 'enable' bit set in the msr
231  */
232 #ifdef CONFIG_KEXEC_CORE
233 static void kvm_crash_shutdown(struct pt_regs *regs)
234 {
235         native_write_msr(msr_kvm_system_time, 0, 0);
236         kvm_disable_steal_time();
237         native_machine_crash_shutdown(regs);
238 }
239 #endif
240 
241 static void kvm_shutdown(void)
242 {
243         native_write_msr(msr_kvm_system_time, 0, 0);
244         kvm_disable_steal_time();
245         native_machine_shutdown();
246 }
247 
248 void __init kvmclock_init(void)
249 {
250         struct pvclock_vcpu_time_info *vcpu_time;
251         unsigned long mem;
252         int size, cpu;
253         u8 flags;
254 
255         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
256 
257         if (!kvm_para_available())
258                 return;
259 
260         if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
261                 msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
262                 msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
263         } else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
264                 return;
265 
266         printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
267                 msr_kvm_system_time, msr_kvm_wall_clock);
268 
269         mem = memblock_alloc(size, PAGE_SIZE);
270         if (!mem)
271                 return;
272         hv_clock = __va(mem);
273         memset(hv_clock, 0, size);
274 
275         if (kvm_register_clock("primary cpu clock")) {
276                 hv_clock = NULL;
277                 memblock_free(mem, size);
278                 return;
279         }
280 
281         if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
282                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
283 
284         cpu = get_cpu();
285         vcpu_time = &hv_clock[cpu].pvti;
286         flags = pvclock_read_flags(vcpu_time);
287 
288         kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
289         put_cpu();
290 
291         x86_platform.calibrate_tsc = kvm_get_tsc_khz;
292         x86_platform.get_wallclock = kvm_get_wallclock;
293         x86_platform.set_wallclock = kvm_set_wallclock;
294 #ifdef CONFIG_X86_LOCAL_APIC
295         x86_cpuinit.early_percpu_clock_init =
296                 kvm_setup_secondary_clock;
297 #endif
298         x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
299         x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
300         machine_ops.shutdown  = kvm_shutdown;
301 #ifdef CONFIG_KEXEC_CORE
302         machine_ops.crash_shutdown  = kvm_crash_shutdown;
303 #endif
304         kvm_get_preset_lpj();
305         clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
306         pv_info.name = "KVM";
307 }
308 
309 int __init kvm_setup_vsyscall_timeinfo(void)
310 {
311 #ifdef CONFIG_X86_64
312         int cpu;
313         u8 flags;
314         struct pvclock_vcpu_time_info *vcpu_time;
315         unsigned int size;
316 
317         if (!hv_clock)
318                 return 0;
319 
320         size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
321 
322         cpu = get_cpu();
323 
324         vcpu_time = &hv_clock[cpu].pvti;
325         flags = pvclock_read_flags(vcpu_time);
326 
327         if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
328                 put_cpu();
329                 return 1;
330         }
331 
332         put_cpu();
333 
334         kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
335 #endif
336         return 0;
337 }
338 

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