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Date:   Fri, 14 Feb 2020 23:27:18 +0000
From:   Anchal Agarwal <anchalag@amazon.com>
To:     <tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
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Subject: [RFC PATCH v3 10/12] xen: Introduce wrapper for save/restore sched
 clock offset
Message-ID: <305f20fbf503b637b1a08b7bec543f49271a725a.1581721799.git.anchalag@amazon.com>
References: <cover.1581721799.git.anchalag@amazon.com>
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User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
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Introduce wrappers for save/restore xen_sched_clock_offset to be
used by PM hibernation code to avoid system instability during resume.

Signed-off-by: Anchal Agarwal <anchalag@amazon.com>
---
 arch/x86/xen/time.c    | 15 +++++++++++++--
 arch/x86/xen/xen-ops.h |  2 ++
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 8cf632dda605..eeb6d3d2eaab 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -379,12 +379,23 @@ static const struct pv_time_ops xen_time_ops __initconst = {
 static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
 static u64 xen_clock_value_saved;
 
+/*This is needed to maintain a monotonic clock value during PM hibernation */
+void xen_save_sched_clock_offset(void)
+{
+	xen_clock_value_saved = xen_clocksource_read() - xen_sched_clock_offset;
+}
+
+void xen_restore_sched_clock_offset(void)
+{
+	xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
+}
+
 void xen_save_time_memory_area(void)
 {
 	struct vcpu_register_time_memory_area t;
 	int ret;
 
-	xen_clock_value_saved = xen_clocksource_read() - xen_sched_clock_offset;
+	xen_save_sched_clock_offset();
 
 	if (!xen_clock)
 		return;
@@ -426,7 +437,7 @@ void xen_restore_time_memory_area(void)
 out:
 	/* Need pvclock_resume() before using xen_clocksource_read(). */
 	pvclock_resume();
-	xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
+	xen_restore_sched_clock_offset();
 }
 
 static void xen_setup_vsyscall_time_info(void)
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index d84c357994bd..9f49124df033 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -72,6 +72,8 @@ void xen_save_time_memory_area(void);
 void xen_restore_time_memory_area(void);
 void xen_init_time_ops(void);
 void xen_hvm_init_time_ops(void);
+void xen_save_sched_clock_offset(void);
+void xen_restore_sched_clock_offset(void);
 
 irqreturn_t xen_debug_interrupt(int irq, void *dev_id);
 
-- 
2.24.1.AMZN