When the PF and VF drivers both support flexible rx descriptors and have
negotiated the VIRTCHNL_VF_OFFLOAD_RX_FLEX_DESC capability, the VF driver
queries the PF for the list of supported descriptor formats
(VIRTCHNL_OP_GET_SUPPORTED_RXDIDS). The PF driver is supposed to set the
supported_rxdids bits that correspond to the descriptor formats the
firmware implements. The legacy 32-byte rx desc format is always
supported, even though it is not expressed in GLFLXP_RXDID_FLAGS.

The ice driver does not advertise the legacy 32-byte rx desc support,
which leads to this failure to bring up the VF using the Intel
out-of-tree iavf driver:
 iavf 0000:41:01.0: PF does not list support for default Rx descriptor format
 ...
 iavf 0000:41:01.0: PF returned error -5 (VIRTCHNL_STATUS_ERR_PARAM) to our request 6

The in-tree iavf driver does not expose this bug, because it does not
yet implement VIRTCHNL_VF_OFFLOAD_RX_FLEX_DESC.

The ice driver must always set the ICE_RXDID_LEGACY_1 bit in
supported_rxdids. The Intel out-of-tree ice driver and the ice driver in
DPDK both do this.

I copied this piece of the code and the comment text from the Intel
out-of-tree driver.

Fixes: e753df8f ("ice: Add support Flex RXD")
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://lore.kernel.org/r/20230920115439.61172-1-mschmidt@redhat.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>