Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c84f1e0..befbdd8 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -28,7 +28,7 @@
 
 #include "xen-ops.h"
 
-/* Xen may fire a timer up to this many ns early */
+/* Minimum amount of time until next clock event fires */
 #define TIMER_SLOP	100000
 
 static u64 xen_sched_clock_offset __read_mostly;
@@ -212,7 +212,7 @@
 	return 0;
 }
 
-static const struct clock_event_device xen_timerop_clockevent = {
+static struct clock_event_device xen_timerop_clockevent __ro_after_init = {
 	.name			= "xen",
 	.features		= CLOCK_EVT_FEAT_ONESHOT,
 
@@ -273,7 +273,7 @@
 	return ret;
 }
 
-static const struct clock_event_device xen_vcpuop_clockevent = {
+static struct clock_event_device xen_vcpuop_clockevent __ro_after_init = {
 	.name = "xen",
 	.features = CLOCK_EVT_FEAT_ONESHOT,
 
@@ -361,8 +361,6 @@
 {
 	int cpu;
 
-	pvclock_resume();
-
 	if (xen_clockevent != &xen_vcpuop_clockevent)
 		return;
 
@@ -379,12 +377,15 @@
 };
 
 static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
+static u64 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;
+
 	if (!xen_clock)
 		return;
 
@@ -404,7 +405,7 @@
 	int ret;
 
 	if (!xen_clock)
-		return;
+		goto out;
 
 	t.addr.v = &xen_clock->pvti;
 
@@ -421,6 +422,11 @@
 	if (ret != 0)
 		pr_notice("Cannot restore secondary vcpu_time_info (err %d)",
 			  ret);
+
+out:
+	/* Need pvclock_resume() before using xen_clocksource_read(). */
+	pvclock_resume();
+	xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
 }
 
 static void xen_setup_vsyscall_time_info(void)
@@ -513,7 +519,7 @@
 void __init xen_init_time_ops(void)
 {
 	xen_sched_clock_offset = xen_clocksource_read();
-	pv_time_ops = xen_time_ops;
+	pv_ops.time = xen_time_ops;
 
 	x86_init.timers.timer_init = xen_time_init;
 	x86_init.timers.setup_percpu_clockev = x86_init_noop;
@@ -555,7 +561,7 @@
 	}
 
 	xen_sched_clock_offset = xen_clocksource_read();
-	pv_time_ops = xen_time_ops;
+	pv_ops.time = xen_time_ops;
 	x86_init.timers.setup_percpu_clockev = xen_time_init;
 	x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
 
@@ -564,3 +570,17 @@
 	x86_platform.set_wallclock = xen_set_wallclock;
 }
 #endif
+
+/* Kernel parameter to specify Xen timer slop */
+static int __init parse_xen_timer_slop(char *ptr)
+{
+	unsigned long slop = memparse(ptr, NULL);
+
+	xen_timerop_clockevent.min_delta_ns = slop;
+	xen_timerop_clockevent.min_delta_ticks = slop;
+	xen_vcpuop_clockevent.min_delta_ns = slop;
+	xen_vcpuop_clockevent.min_delta_ticks = slop;
+
+	return 0;
+}
+early_param("xen_timer_slop", parse_xen_timer_slop);