x86/shim: suspend and resume platform time correctly

Similarly to S3, platform time needs to be saved on guest suspend
and restored on resume respectively. This should account for expected
jumps in PV clock counter value after resume. time_suspend/resume()
are safe to use in PVH setting as is since any existing operations
with PIT/HPET that they do would simply be ignored if PIT/HPET is
not present.

Additionally, add resume callback for Xen PV clocksource to avoid
its breakage on migration.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
master commit: a7a3ecd82e289a9a2ecc1d3b5128580e0b577cc7
master date: 2020-02-14 18:01:52 +0000

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index b75975b8534f4e833bc4c1f986ac62b2c67b7e62..1501fc0632ddfc327660433390dc458b45b9be22 100644 (file)
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -325,9 +325,13 @@ int pv_shim_shutdown(uint8_t reason)
         if ( v != current )
             vcpu_pause_by_systemcontroller(v);
 
+    /* Prepare timekeeping code to suspend.*/
+    time_suspend();
+
     rc = xen_hypercall_shutdown(SHUTDOWN_suspend);
     if ( rc )
     {
+        time_resume();
         for_each_vcpu ( d, v )
             if ( v != current )
                 vcpu_unpause_by_systemcontroller(v);
@@ -335,8 +339,9 @@ int pv_shim_shutdown(uint8_t reason)
         return rc;
     }
 
-    /* Resume the shim itself first. */
+    /* Resume the shim itself and timekeeping first. */
     hypervisor_resume();
+    time_resume();
 
     /*
      * ATM there's nothing Xen can do if the console/store pfn changes,

diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 09692bcdb78ccf502cc8e7c479ae7ab56763e7d4..9b28128baf82449a9ada7f6b568beebf366669ac 100644 (file)
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -565,6 +565,7 @@ static struct platform_timesource __initdata plt_tsc =
  *
  * Xen clock source is a variant of TSC source.
  */
+static uint64_t xen_timer_last;
 
 static uint64_t xen_timer_cpu_frequency(void)
 {
@@ -610,7 +611,6 @@ static uint64_t read_xen_timer(void)
     uint32_t version;
     uint64_t ret;
     uint64_t last;
-    static uint64_t last_value;
 
     do {
         version = info->version & ~1;
@@ -626,20 +626,26 @@ static uint64_t read_xen_timer(void)
 
     /* Maintain a monotonic global value */
     do {
-        last = read_atomic(&last_value);
+        last = read_atomic(&xen_timer_last);
         if ( ret < last )
             return last;
-    } while ( unlikely(cmpxchg(&last_value, last, ret) != last) );
+    } while ( unlikely(cmpxchg(&xen_timer_last, last, ret) != last) );
 
     return ret;
 }
 
+static void resume_xen_timer(struct platform_timesource *pts)
+{
+    write_atomic(&xen_timer_last, 0);
+}
+
 static struct platform_timesource __initdata plt_xen_timer =
 {
     .id = "xen",
     .name = "XEN PV CLOCK",
     .read_counter = read_xen_timer,
     .init = init_xen_timer,
+    .resume = resume_xen_timer,
     .counter_bits = 63,
 };
 #endif