This `len` field describes the amount of bytes
*written* by the device. It is used to prevent
the driver from reading buffer memory that wasn't
really written to - it could contain either
leftover values from previous requests or even
be completely unitialized.
In a couple of invalid-request error conditions
we still write the VIRTIO_BLK_S_UNSUPP response while
returning used_len == 0, but that's fine. A properly
written driver will likely handle both of these cases
the same way.
Change-Id: I8e9f3a8051561096e2ee755122d534b4ffd94db1
Signed-off-by: Dariusz Stojaczyk <dariuszx.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/393963
Reviewed-by: Pawel Kaminski <pawelx.kaminski@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
Reviewed-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
60c1cd75dc