Commit f94c8d11699759 ("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.
Fixes: f94c8d11699759 ("sched/clock, x86/tsc: Rework the x86 'unstable' sched_clock() interface") Cc: stable@vger.kernel.org # 4.11 Reported-by: Hans van Kranenburg hans@knorrie.org Signed-off-by: Juergen Gross jgross@suse.com --- arch/x86/xen/time.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c index 72bf446c3fee..3c1dfdf26284 100644 --- a/arch/x86/xen/time.c +++ b/arch/x86/xen/time.c @@ -379,12 +379,15 @@ 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 +407,7 @@ void xen_restore_time_memory_area(void) int ret;
if (!xen_clock) - return; + goto out;
t.addr.v = &xen_clock->pvti;
@@ -421,6 +424,11 @@ 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)