[XENVBD PATCH 2/3] Reduce the strength of Xen barriers on x86

[Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>]

x86 is TSO and only needs a compiler barrier as read/write barriers.

Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>
---
 include/xen-types.h | 9 +++++++++
 src/xenvbd/ring.c   | 3 ---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/xen-types.h b/include/xen-types.h
index 40f7c27..0f53af3 100644
--- a/include/xen-types.h
+++ b/include/xen-types.h
@@ -47,4 +47,13 @@ typedef USHORT  uint16_t;
 typedef ULONG   uint32_t;
 typedef ULONG64 uint64_t;
 
+#define xen_mb()    KeMemoryBarrier()
+#if defined(_M_IX86) || defined(_M_X64)
+#define xen_wmb()   KeMemoryBarrierWithoutFence()
+#define xen_rmb()   KeMemoryBarrierWithoutFence()
+#else
+#define xen_wmb()   KeMemoryBarrier()
+#define xen_rmb()   KeMemoryBarrier()
+#endif
+
 #endif  // _XEN_TYPES_H
diff --git a/src/xenvbd/ring.c b/src/xenvbd/ring.c
index 5a8f236..205e93a 100644
--- a/src/xenvbd/ring.c
+++ b/src/xenvbd/ring.c
@@ -57,9 +57,6 @@
 #define XENVBD_MAX_RING_PAGE_ORDER  (4)
 #define XENVBD_MAX_RING_PAGES       (1 << XENVBD_MAX_RING_PAGE_ORDER)
 
-#define xen_mb  KeMemoryBarrier
-#define xen_wmb KeMemoryBarrier
-
 typedef struct _XENVBD_BLKIF_RING {
     PXENVBD_RING                    Ring;
     ULONG                           Index;
-- 
2.54.0.windows.1



--
Ngoc Tu Dinh | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

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