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

["Stanisław Kardach" <kda@semihalf.com>]

On Wed, Jun 8, 2022 at 10:42 AM David Marchand
<david.marchand@redhat.com> wrote:
>
> 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.
If you mean the modified entry in the known_issues, I've added it at
Heinrich's request, although I agree I should have placed it in 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.
I have just checked with fedora/36 docker and it seems that only gcc
and binutils packages are there but stdlib isn't. Hence meson fails at
basic checks because it can't find "stdio.h". So that's a bug to post
to Fedora I believe.
What does work in terms of cross-compiling is using a
riscv-gnu-toolchain tarball + modified cross-file (i.e. from here:
https://github.com/riscv-collab/riscv-gnu-toolchain/releases/tag/2022.06.03).
That most likely won't work for building RPMs but for static
compilations it might be enough.
Or you could use a Ubuntu docker and cross-compile there (though the
same problem as before):
  docker run -v /path/to/dpdk:/opt/dpdk -it ubuntu:jammy /bin/bash
Or a VM as Heinrich suggested.
>
> At least the compilation in GHA works.
That's because I've used Ubuntu as a base, which has a proper
toolchain setup. Also riscv-gnu-toolchain project targets Ubuntu, so
that helps.
>
>
> - 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 think I'll rename the config file.
In theory, the man file of pkg-config
(https://linux.die.net/man/1/pkg-config) mentions the default
searching path as prefix/lib/pkgconfig. Prefix being
/usr/riscv64-linux-gnu the generic location should be
/usr/riscv64-linux-gnu/lib/pkgconfig but Ubuntu doesn't follow that.
There are no RISC-V cross-libs offering pkg-config neither in Ubuntu
or Fedora so I can't really tell what's the best path to use. Though
that also means we won't hit this issue for some time.
>
>
> - I adjusted some coding style in some asm and some indentation and
> wording in meson.
Thanks!
>
>
> - 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?
I'm testing a fix for this. I have not taken C++ type conversion rules
into account.
>
>
> - There was a patch from Heinrich about native compilation, can you review it?
I see it was merged but your question from that thread still stands.
I'm compiling native now to check.
>

>
> --
> David Marchand
>