Hi, Honnappa We discussed the barrier here: http://patches.dpdk.org/project/dpdk/patch/[email protected]/
(BTW, it is good practice to keep the reference to previous patch versions below Commit Message of the next ones). This barrier is not about compiler ordering, it is about external HW agent memory action completions. So, I'm not sure the rte_atomic_thread_fence() is safe for x86 - patch impacts x86 as well. With best regards, Slava > -----Original Message----- > From: Honnappa Nagarahalli <[email protected]> > Sent: Tuesday, August 30, 2022 23:01 > To: [email protected]; [email protected]; [email protected]; Matan > Azrad <[email protected]>; Shahaf Shuler <[email protected]>; Slava > Ovsiienko <[email protected]> > Cc: [email protected]; Matan Azrad <[email protected]>; [email protected] > Subject: [PATCH v2] net/mlx5: use just sufficient barrier for Arm platforms > > cqe->op_own indicates if the CQE is owned by the NIC. The rest of > the fields in CQE should be read only after op_own is read. On Arm platforms > using "dmb ishld" is sufficient to enforce this. > > Fixes: 88c0733535d6 ("net/mlx5: extend Rx completion with error handling") > Cc: [email protected] > Cc: [email protected] > > Signed-off-by: Honnappa Nagarahalli <[email protected]> > Reviewed-by: Ruifeng Wang <[email protected]> > --- > drivers/common/mlx5/mlx5_common.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/common/mlx5/mlx5_common.h > b/drivers/common/mlx5/mlx5_common.h > index 5028a05b49..ac2e85b15f 100644 > --- a/drivers/common/mlx5/mlx5_common.h > +++ b/drivers/common/mlx5/mlx5_common.h > @@ -195,7 +195,11 @@ check_cqe(volatile struct mlx5_cqe *cqe, const uint16_t > cqes_n, > > if (unlikely((op_owner != (!!(idx))) || (op_code == > MLX5_CQE_INVALID))) > return MLX5_CQE_STATUS_HW_OWN; > - rte_io_rmb(); > + /* Prevent speculative reading of other fields in CQE until > + * CQE is valid. > + */ > + rte_atomic_thread_fence(__ATOMIC_ACQUIRE); > + > if (unlikely(op_code == MLX5_CQE_RESP_ERR || > op_code == MLX5_CQE_REQ_ERR)) > return MLX5_CQE_STATUS_ERR; > -- > 2.17.1
