idpf: add read memory barrier when checking descriptor done bit

[ Upstream commit 396f0165672c6a74d7379027d344b83b5f05948c ]

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>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

0 files changed, 0 insertions, 0 deletions