From a9eb63495c7cec7a3e4aebd2dc93225c685b693b Mon Sep 17 00:00:00 2001 From: Emil Tantilov Date: Fri, 24 Jan 2025 13:32:03 -0800 Subject: [PATCH] idpf: add read memory barrier when checking descriptor done bit Add read memory barrier to ensure the order of operations when accessing control queue descriptors. Specifically, we want to avoid cases where loads can be reordered: 1. Load #1 is dispatched to read descriptor flags. 2. Load #2 is dispatched to read some other field from the descriptor. 3. Load #2 completes, accessing memory/cache at a point in time when the DD flag is zero. 4. NIC DMA overwrites the descriptor, now the DD flag is one. 5. Any fields loaded before step 4 are now inconsistent with the actual descriptor state. Add read memory barrier between steps 1 and 2, so that load #2 is not executed until load #1 has completed. Fixes: 8077c727561a ("idpf: add controlq init and reset checks") Reviewed-by: Przemek Kitszel Reviewed-by: Sridhar Samudrala Suggested-by: Lance Richardson Signed-off-by: Emil Tantilov Tested-by: Krishneil Singh Signed-off-by: Tony Nguyen Signed-off-by: NipaLocal --- drivers/net/ethernet/intel/idpf/idpf_controlq.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/ethernet/intel/idpf/idpf_controlq.c b/drivers/net/ethernet/intel/idpf/idpf_controlq.c index 4849590a5591..b28991dd1870 100644 --- a/drivers/net/ethernet/intel/idpf/idpf_controlq.c +++ b/drivers/net/ethernet/intel/idpf/idpf_controlq.c @@ -376,6 +376,9 @@ int idpf_ctlq_clean_sq(struct idpf_ctlq_info *cq, u16 *clean_count, if (!(le16_to_cpu(desc->flags) & IDPF_CTLQ_FLAG_DD)) break; + /* Ensure no other fields are read until DD flag is checked */ + dma_rmb(); + /* strip off FW internal code */ desc_err = le16_to_cpu(desc->ret_val) & 0xff; @@ -563,6 +566,9 @@ int idpf_ctlq_recv(struct idpf_ctlq_info *cq, u16 *num_q_msg, if (!(flags & IDPF_CTLQ_FLAG_DD)) break; + /* Ensure no other fields are read until DD flag is checked */ + dma_rmb(); + q_msg[i].vmvf_type = (flags & (IDPF_CTLQ_FLAG_FTYPE_VM | IDPF_CTLQ_FLAG_FTYPE_PF)) >>