xen: Fix x86 sched_clock() interface for xen

Commit f94c8d1 ("sched/clock, x86/tsc: Rework the x86 'unstable' sched_clock() interface") broke Xen guest time handling across migration: [ 187.249951] Freezing user space processes ... (elapsed 0.001 seconds) done. [ 187.251137] OOM killer disabled. [ 187.251137] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done. [ 187.252299] suspending xenstore... [ 187.266987] xen:grant_table: Grant tables using version 1 layout [18446743811.706476] OOM killer enabled. [18446743811.706478] Restarting tasks ... done. [18446743811.720505] Setting capacity to 16777216 Fix that by setting xen_sched_clock_offset at resume time to ensure a monotonic clock value. [boris: replaced pr_info() with pr_info_once() in xen_callback_vector() to avoid printing with incorrect timestamp during resume (as we haven't re-adjusted the clock yet)] Fixes: f94c8d1 ("sched/clock, x86/tsc: Rework the x86 'unstable' sched_clock() interface") Cc: <[email protected]> # 4.11 Reported-by: Hans van Kranenburg <[email protected]> Signed-off-by: Juergen Gross <[email protected]> Tested-by: Hans van Kranenburg <[email protected]> Signed-off-by: Boris Ostrovsky <[email protected]>
btm · Jan 16, 2019 · 867cefb · 867cefb
1 parent b471109
commit 867cefb
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Showing 2 changed files with 10 additions and 4 deletions.
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
@@ -361,8 +361,6 @@ void xen_timer_resume(void)
 {
 	int cpu;
 
-	pvclock_resume();
-
 	if (xen_clockevent != &xen_vcpuop_clockevent)
 		return;
 
@@ -379,12 +377,15 @@ 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;
 
 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 @@ void xen_restore_time_memory_area(void)
 	int ret;
 
 	if (!xen_clock)
-		return;
+		goto out;
 
 	t.addr.v = &xen_clock->pvti;
 
@@ -421,6 +422,11 @@ void xen_restore_time_memory_area(void)
 	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)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
@@ -1650,7 +1650,7 @@ void xen_callback_vector(void)
 			xen_have_vector_callback = 0;
 			return;
 		}
-		pr_info("Xen HVM callback vector for event delivery is enabled\n");
+		pr_info_once("Xen HVM callback vector for event delivery is enabled\n");
 		alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR,
 				xen_hvm_callback_vector);
 	}