Re: [PATCH v4 0/8] Introduce support for RISC-V architecture

[David Marchand <david.marchand@redhat.com>]

On Tue, May 31, 2022 at 4:14 PM Stanislaw Kardach <kda@semihalf.com> wrote:
>
> This patchset adds support for building and running DPDK on 64bit RISC-V
> architecture. The initial support targets rv64gc (rv64imafdc) ISA and
> was tested on SiFive Unmatched development board with the Freedom U740
> SoC running Linux (freedom-u-sdk based kernel).
> I have tested this codebase using DPDK unit and perf tests as well as
> test-pmd, l2fwd and l3fwd examples.
> The NIC attached to the DUT was Intel X520-DA2 which uses ixgbe PMD.
> On the UIO side, since U740 does not have an IOMMU, I've used igb_uio,
> uio_pci_generic and vfio-pci noiommu drivers.
>
> Functional verification done using meson tests. fast-tests suite passing with
> the default config.
>
> PMD verification done using a Intel x520-DA2 NIC (ixgbe) 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.
>
> The i40e PMD driver is disabled on RISC-V as the rv64gc ISA has no vector
> operations.
>
> RISCV support is currently limited to Linux as the time measurement frequency
> discovery is tied to reading a device-tree node via procfs.
>
> Clang compilation currently not supported due to issues with missing relocation
> relaxation.
>
> Commit 1 introduces EAL and build system support for RISC-V architecture
>    as well as documentation updates.
> Commits 2-5 add missing defines and stubs to enable RISC-V operation in
>    non-EAL parts.
> Commit 6 adds RISC-V specific cpuflags test.
> Commits 7-8 add RISC-V build testing to test-meson-builds.sh and github CI.

Overall, the series lgtm.
It did not get much reviews, but the porting is straightforward and
clean enough.

I'm waiting for some compilation to finish and I will merge it for 22.07-rc1.


Some comments that will probably require some followup patches for rc2:

- I removed the known issue about --no-huge from the EAL patch.
This seems to be a generic issue that does not block the RISC V port
and can be re-submitted as a separate patch.


- I had some trouble with finding a right toolchain for test-meson-builds.sh.
The mentionned toolchains in the cross build guide don't work for me on FC36.
I managed to cross compile with a Bootlin toolchain, though I had to
adjust the cross compilation file.
I'll probably end up compiling my own toolchain later unless you have
a better idea.

At least the compilation in GHA works.


- The hardcoded pkg-config path in config/riscv/riscv64_linux_gcc does
not seem generic.
It is probably not a big issue, but I'd rather move it to a Ubuntu
specific cross compile meson file.
WDYT?


- I adjusted some coding style in some asm and some indentation and
wording in meson.


- The cross compilation guide mentions using
crossbuild-essential-riscv64 for Ubuntu.
We should switch to it in GHA.
Though after trying myself, there is an issue in the C++ headers check
in GHA for some acl header including rte_vect.h.
Can you have a look?


- There was a patch from Heinrich about native compilation, can you review it?


-- 
David Marchand