xen/time: use READ_ONCE

Use READ_ONCE through the code, rather than explicit barriers.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/drivers/xen/time.c b/drivers/xen/time.c
index 433fe247c5ff..71078425c9ea 100644
--- a/drivers/xen/time.c
+++ b/drivers/xen/time.c
@@ -25,7 +25,7 @@ static u64 get64(const u64 *p)
 
         if (BITS_PER_LONG < 64) {
                 u32 *p32 = (u32 *)p;
-                u32 h, l;
+                u32 h, l, h2;
 
                 /*
                  * Read high then low, and then make sure high is
@@ -34,15 +34,14 @@ static u64 get64(const u64 *p)
                  * XXX some clean way to make this endian-proof?
                  */
                 do {
-                        h = p32[1];
-                        barrier();
-                        l = p32[0];
-                        barrier();
-                } while (p32[1] != h);
+                        h = READ_ONCE(p32[1]);
+                        l = READ_ONCE(p32[0]);
+                        h2 = READ_ONCE(p32[1]);
+                } while(h2 != h);
 
                 ret = (((u64)h) << 32) | l;
         } else
-                ret = *p;
+                ret = READ_ONCE(*p);
 
         return ret;
 }
@@ -66,9 +65,7 @@ void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
          */
         do {
                 state_time = get64(&state->state_entry_time);
-                barrier();
-                *res = *state;
-                barrier();
+                *res = READ_ONCE(*state);
         } while (get64(&state->state_entry_time) != state_time);
 }