time: export time information for KVM pvclock

As suggested by John, export time data similarly to how its done by vsyscall support. This allows KVM to retrieve necessary information to implement vsyscall support in KVM guests. Acked-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

time: export time information for KVM pvclock
As suggested by John, export time data similarly to how its done by vsyscall support. This allows KVM to retrieve necessary information to implement vsyscall support in KVM guests. Acked-by: John Stultz <johnstul@us.ibm.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Marcelo Tosatti
1 parent 886b470cb1
Showing 2 changed files with 59 additions and 0 deletions Side-by-side Diff
include/linux/pvclock_gtod.h
kernel/time/timekeeping.c
+#ifndef _PVCLOCK_GTOD_H
+#define _PVCLOCK_GTOD_H
+
+#include <linux/notifier.h>
+
+extern int pvclock_gtod_register_notifier(struct notifier_block *nb);
+extern int pvclock_gtod_unregister_notifier(struct notifier_block *nb);
+
+#endif /* _PVCLOCK_GTOD_H */
@@ -21,6 +21,7 @@
 #include <linux/time.h>
 #include <linux/tick.h>
 #include <linux/stop_machine.h>
+#include <linux/pvclock_gtod.h>
  
  
 static struct timekeeper timekeeper;
@@ -180,6 +181,54 @@
 	return nsec + arch_gettimeoffset();
 }
  
+static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
+
+static void update_pvclock_gtod(struct timekeeper *tk)
+{
+	raw_notifier_call_chain(&pvclock_gtod_chain, 0, tk);
+}
+
+/**
+ * pvclock_gtod_register_notifier - register a pvclock timedata update listener
+ *
+ * Must hold write on timekeeper.lock
+ */
+int pvclock_gtod_register_notifier(struct notifier_block *nb)
+{
+	struct timekeeper *tk = &timekeeper;
+	unsigned long flags;
+	int ret;
+
+	write_seqlock_irqsave(&tk->lock, flags);
+	ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
+	/* update timekeeping data */
+	update_pvclock_gtod(tk);
+	write_sequnlock_irqrestore(&tk->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
+
+/**
+ * pvclock_gtod_unregister_notifier - unregister a pvclock
+ * timedata update listener
+ *
+ * Must hold write on timekeeper.lock
+ */
+int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
+{
+	struct timekeeper *tk = &timekeeper;
+	unsigned long flags;
+	int ret;
+
+	write_seqlock_irqsave(&tk->lock, flags);
+	ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
+	write_sequnlock_irqrestore(&tk->lock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
+
 /* must hold write on timekeeper.lock */
 static void timekeeping_update(struct timekeeper *tk, bool clearntp)
 {
@@ -188,6 +237,7 @@
 		ntp_clear();
 	}
 	update_vsyscall(tk);
+	update_pvclock_gtod(tk);
 }
  
 /**
	1	+#ifndef _PVCLOCK_GTOD_H
	2	+#define _PVCLOCK_GTOD_H
	3	+
	4	+#include <linux/notifier.h>
	5	+
	6	+extern int pvclock_gtod_register_notifier(struct notifier_block *nb);
	7	+extern int pvclock_gtod_unregister_notifier(struct notifier_block *nb);
	8	+
	9	+#endif /* _PVCLOCK_GTOD_H */
...	...	@@ -21,6 +21,7 @@
21	21	#include <linux/time.h>
22	22	#include <linux/tick.h>
23	23	#include <linux/stop_machine.h>
	24	+#include <linux/pvclock_gtod.h>
24	25
25	26
26	27	static struct timekeeper timekeeper;
...	...	@@ -180,6 +181,54 @@
180	181	return nsec + arch_gettimeoffset();
181	182	}
182	183
	184	+static RAW_NOTIFIER_HEAD(pvclock_gtod_chain);
	185	+
	186	+static void update_pvclock_gtod(struct timekeeper *tk)
	187	+{
	188	+ raw_notifier_call_chain(&pvclock_gtod_chain, 0, tk);
	189	+}
	190	+
	191	+/**
	192	+ * pvclock_gtod_register_notifier - register a pvclock timedata update listener
	193	+ *
	194	+ * Must hold write on timekeeper.lock
	195	+ */
	196	+int pvclock_gtod_register_notifier(struct notifier_block *nb)
	197	+{
	198	+ struct timekeeper *tk = &timekeeper;
	199	+ unsigned long flags;
	200	+ int ret;
	201	+
	202	+ write_seqlock_irqsave(&tk->lock, flags);
	203	+ ret = raw_notifier_chain_register(&pvclock_gtod_chain, nb);
	204	+ /* update timekeeping data */
	205	+ update_pvclock_gtod(tk);
	206	+ write_sequnlock_irqrestore(&tk->lock, flags);
	207	+
	208	+ return ret;
	209	+}
	210	+EXPORT_SYMBOL_GPL(pvclock_gtod_register_notifier);
	211	+
	212	+/**
	213	+ * pvclock_gtod_unregister_notifier - unregister a pvclock
	214	+ * timedata update listener
	215	+ *
	216	+ * Must hold write on timekeeper.lock
	217	+ */
	218	+int pvclock_gtod_unregister_notifier(struct notifier_block *nb)
	219	+{
	220	+ struct timekeeper *tk = &timekeeper;
	221	+ unsigned long flags;
	222	+ int ret;
	223	+
	224	+ write_seqlock_irqsave(&tk->lock, flags);
	225	+ ret = raw_notifier_chain_unregister(&pvclock_gtod_chain, nb);
	226	+ write_sequnlock_irqrestore(&tk->lock, flags);
	227	+
	228	+ return ret;
	229	+}
	230	+EXPORT_SYMBOL_GPL(pvclock_gtod_unregister_notifier);
	231	+
183	232	/* must hold write on timekeeper.lock */
184	233	static void timekeeping_update(struct timekeeper *tk, bool clearntp)
185	234	{
...	...	@@ -188,6 +237,7 @@
188	237	ntp_clear();
189	238	}
190	239	update_vsyscall(tk);
	240	+ update_pvclock_gtod(tk);
191	241	}
192	242
193	243	/**