[patch 14/15] time: export time information for KVM pvclock

From: Marcelo Tosatti <mtosatti@redhat.com>
To: kvm@vger.kernel.org
Cc: johnstul@us.ibm.com, jeremy@goop.org,
	Marcelo Tosatti <mtosatti@redhat.com>
Subject: [patch 14/15] time: export time information for KVM pvclock
Date: Tue, 16 Oct 2012 14:56:33 -0300	[thread overview]
Message-ID: <20121016180137.923799800@redhat.com> (raw)
In-Reply-To: 20121016175619.194848607@redhat.com

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As suggested by John, export time data similarly to how its
by vsyscall support. This allows KVM to retrieve necessary
information to implement vsyscall support in KVM guests.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: vsyscall/include/linux/pvclock_gtod.h
===================================================================

--- /dev/null
+++ vsyscall/include/linux/pvclock_gtod.h
@@ -0,0 +1,23 @@
+#ifndef _PVCLOCK_GTOD_H
+#define _PVCLOCK_GTOD_H
+
+#include <linux/clocksource.h>
+
+struct pvclock_gtod_data {
+	seqcount_t	seq;
+
+	struct { /* extract of a clocksource struct */
+		int vclock_mode;
+		cycle_t	cycle_last;
+		cycle_t	mask;
+		u32	mult;
+		u32	shift;
+	} clock;
+
+	/* open coded 'struct timespec' */
+	u64		monotonic_time_snsec;
+	time_t		monotonic_time_sec;
+};
+extern struct pvclock_gtod_data pvclock_gtod_data;
+
+#endif /* _PVCLOCK_GTOD_H */
Index: vsyscall/kernel/time/timekeeping.c
===================================================================
--- vsyscall.orig/kernel/time/timekeeping.c
+++ vsyscall/kernel/time/timekeeping.c
@@ -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 +181,37 @@ static inline s64 timekeeping_get_ns_raw
 	return nsec + arch_gettimeoffset();
 }
 
+struct pvclock_gtod_data pvclock_gtod_data;
+EXPORT_SYMBOL_GPL(pvclock_gtod_data);
+
+static void update_pvclock_gtod(struct timekeeper *tk)
+{
+	struct pvclock_gtod_data *vdata = &pvclock_gtod_data;
+
+	write_seqcount_begin(&vdata->seq);
+
+	/* copy vsyscall data */
+	vdata->clock.vclock_mode	= tk->clock->archdata.vclock_mode;
+	vdata->clock.cycle_last		= tk->clock->cycle_last;
+	vdata->clock.mask		= tk->clock->mask;
+	vdata->clock.mult		= tk->mult;
+	vdata->clock.shift		= tk->shift;
+
+	vdata->monotonic_time_sec	= tk->xtime_sec
+					+ tk->wall_to_monotonic.tv_sec;
+	vdata->monotonic_time_snsec	= tk->xtime_nsec
+					+ (tk->wall_to_monotonic.tv_nsec
+						<< tk->shift);
+	while (vdata->monotonic_time_snsec >=
+					(((u64)NSEC_PER_SEC) << tk->shift)) {
+		vdata->monotonic_time_snsec -=
+					((u64)NSEC_PER_SEC) << tk->shift;
+		vdata->monotonic_time_sec++;
+	}
+
+	write_seqcount_end(&vdata->seq);
+}
+
 /* must hold write on timekeeper.lock */
 static void timekeeping_update(struct timekeeper *tk, bool clearntp)
 {
@@ -188,6 +220,7 @@ static void timekeeping_update(struct ti
 		ntp_clear();
 	}
 	update_vsyscall(tk);
+	update_pvclock_gtod(tk);
 }
 
 /**


