net/ixgbe: add vector stubs for RISC-V

Re-use vector processing stubs in ixgbe PMD defined for PPC for RISC-V.
This enables ixgbe PMD usage in scalar mode on this architecture.

The ixgbe PMD driver was validated with Intel X520-DA2 NIC and the
test-pmd application. Packet transfer checked using all UIO drivers
available for non-IOMMU platforms: uio_pci_generic, vfio-pci noiommu and
igb_uio.

Sponsored-by: Frank Zhao <frank.zhao@starfivetech.com>
Sponsored-by: Sam Grove <sam.grove@sifive.com>
Signed-off-by: Stanislaw Kardach <kda@semihalf.com>

doc/guides/nics/features/ixgbe.ini

@@ -52,6 +52,7 @@ FreeBSD              = Y
 Linux                = Y
 Windows              = Y
 ARMv8                = Y
+rv64                 = Y
 x86-32               = Y
 x86-64               = Y
 

drivers/net/ixgbe/ixgbe_rxtx.c

@@ -5957,8 +5957,8 @@ ixgbe_config_rss_filter(struct rte_eth_dev *dev,
 	return 0;
 }
 
-/* Stubs needed for linkage when RTE_ARCH_PPC_64 is set */
-#if defined(RTE_ARCH_PPC_64)
+/* Stubs needed for linkage when RTE_ARCH_PPC_64 or RTE_ARCH_RISCV is set */
+#if defined(RTE_ARCH_PPC_64) || defined(RTE_ARCH_RISCV)
 int
 ixgbe_rx_vec_dev_conf_condition_check(struct rte_eth_dev __rte_unused *dev)
 {

drivers/net/ixgbe/meson.build

@@ -1,12 +1,6 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # Copyright(c) 2017 Intel Corporation
 
-if arch_subdir == 'riscv'
-    build = false
-    reason = 'not supported on RISC-V'
-    subdir_done()
-endif
-
 cflags += ['-DRTE_LIBRTE_IXGBE_BYPASS']
 
 subdir('base')