The host driver should do a wmb() before it updates the SQ tail doorbell
to ensure that any writes to the SQ are guaranteed to be visible if a
doorbell update is visible (a store-release) - and indeed, this is what
the Linux NVMe driver does.
Therefore, we require a rmb() after we read the tail doorbell in order
to synchronise properly with the host driver (we need a load-acquire),
and guarantee that the updates to the SQ are visisble to us.
Signed-off-by: Andreas Economides <andreas.economides@nutanix.com>
Change-Id: I57eb1e1f0dfb1091a8f10f40f8ee0e2604d9268c
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/9514
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
93db90f7f3