[Xen-changelog] [xen stable-4.12] x86/shim: suspend and resume platform time correctly

[patchbot@xxxxxxx]

commit c03afaef8f4b8ca9106ebe7e272439e5650cb3c3
Author:     Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
AuthorDate: Thu Mar 5 11:22:20 2020 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Mar 5 11:22:20 2020 +0100

    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@xxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    master commit: a7a3ecd82e289a9a2ecc1d3b5128580e0b577cc7
    master date: 2020-02-14 18:01:52 +0000
---
 xen/arch/x86/pv/shim.c |  7 ++++++-
 xen/arch/x86/time.c    | 12 +++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index b75975b853..1501fc0632 100644
--- 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 09692bcdb7..9b28128baf 100644
--- 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
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.12

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