@@ -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)) >>
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 <przemyslaw.kitszel@intel.com> Reviewed-by: Sridhar Samudrala <sridhar.samudrala@intel.com> Suggested-by: Lance Richardson <rlance@google.com> Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com> --- Changelog v2: - Rewrote comment to fit on a single line - Added new line as separator - Updated last sentence in commit message to include load # v1: https://lore.kernel.org/intel-wired-lan/20241115021618.20565-1-emil.s.tantilov@intel.com/ --- drivers/net/ethernet/intel/idpf/idpf_controlq.c | 6 ++++++ 1 file changed, 6 insertions(+)