[Xen-devel] [PATCH v2] pvcalls-front: 64-bit align flags

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

We are using test_and_* operations on the status and flag fields of
struct sock_mapping. However, these functions require the operand to be
64-bit aligned on arm64. Currently, only status is 64-bit aligned.

Make status and flags explicitly 64-bit aligned.

Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>

---
Changes in v2:
- use __attribute__((aligned(8)))
- add comments

diff --git a/drivers/xen/pvcalls-front.c b/drivers/xen/pvcalls-front.c
index ca5b773..582929e 100644
--- a/drivers/xen/pvcalls-front.c
+++ b/drivers/xen/pvcalls-front.c
@@ -73,20 +73,25 @@ struct sock_mapping {
                        wait_queue_head_t inflight_conn_req;
                } active;
                struct {
-               /* Socket status */
+               /*
+                * Socket status, needs to be 64-bit aligned due to the
+                * test_and_* functions which have this requirement on arm64.
+                */
 #define PVCALLS_STATUS_UNINITALIZED  0
 #define PVCALLS_STATUS_BIND          1
 #define PVCALLS_STATUS_LISTEN        2
-                       uint8_t status;
+                       uint8_t status __attribute__((aligned(8)));
                /*
                 * Internal state-machine flags.
                 * Only one accept operation can be inflight for a socket.
                 * Only one poll operation can be inflight for a given socket.
+                * flags needs to be 64-bit aligned due to the test_and_*
+                * functions which have this requirement on arm64.
                 */
 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
 #define PVCALLS_FLAG_POLL_INFLIGHT   1
 #define PVCALLS_FLAG_POLL_RET        2
-                       uint8_t flags;
+                       uint8_t flags __attribute__((aligned(8)));
                        uint32_t inflight_req_id;
                        struct sock_mapping *accept_map;
                        wait_queue_head_t inflight_accept_req;

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