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Subject[PATCH 4.14 64/68] x86/xen/time: Output xen sched_clock time from 0
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Pavel Tatashin <pasha.tatashin@oracle.com>

commit 38669ba205d178d2d38bfd194a196d65a44d5af2 upstream.

It is expected for sched_clock() to output data from 0, when system boots.

Add an offset xen_sched_clock_offset (similarly how it is done in other
hypervisors i.e. kvm_sched_clock_offset) to count sched_clock() from 0,
when time is first initialized.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-14-pasha.tatashin@oracle.com
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/xen/time.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -31,6 +31,8 @@
/* Xen may fire a timer up to this many ns early */
#define TIMER_SLOP 100000

+static u64 xen_sched_clock_offset __read_mostly;
+
/* Get the TSC speed from Xen */
static unsigned long xen_tsc_khz(void)
{
@@ -57,6 +59,11 @@ static u64 xen_clocksource_get_cycles(st
return xen_clocksource_read();
}

+static u64 xen_sched_clock(void)
+{
+ return xen_clocksource_read() - xen_sched_clock_offset;
+}
+
static void xen_read_wallclock(struct timespec *ts)
{
struct shared_info *s = HYPERVISOR_shared_info;
@@ -367,7 +374,7 @@ void xen_timer_resume(void)
}

static const struct pv_time_ops xen_time_ops __initconst = {
- .sched_clock = xen_clocksource_read,
+ .sched_clock = xen_sched_clock,
.steal_clock = xen_steal_clock,
};

@@ -505,6 +512,7 @@ static void __init xen_time_init(void)

void __ref xen_init_time_ops(void)
{
+ xen_sched_clock_offset = xen_clocksource_read();
pv_time_ops = xen_time_ops;

x86_init.timers.timer_init = xen_time_init;
@@ -547,6 +555,7 @@ void __init xen_hvm_init_time_ops(void)
return;
}

+ xen_sched_clock_offset = xen_clocksource_read();
pv_time_ops = xen_time_ops;
x86_init.timers.setup_percpu_clockev = xen_time_init;
x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;

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