From: Palmer Dabbelt <palmer@sifive.com>
To: bjorn.topel@gmail.com
Cc: bjorn.topel@gmail.com, linux-riscv@lists.infradead.org,
davidlee@sifive.com, daniel@iogearbox.net,
netdev@vger.kernel.org
Subject: Re: [RFC PATCH 0/3] RV64G eBPF JIT
Date: Tue, 29 Jan 2019 18:02:47 -0800 (PST) [thread overview]
Message-ID: <mhng-7bbd5b99-85c7-4071-9427-11442b2a0f91@palmer-si-x1c4> (raw)
In-Reply-To: <20190115083518.10149-1-bjorn.topel@gmail.com>
On Tue, 15 Jan 2019 00:35:15 PST (-0800), bjorn.topel@gmail.com wrote:
> Hi!
>
> I've been hacking on a RV64G eBPF JIT compiler, and would like some
> feedback.
>
> Codewise, it needs some refactoring. Currently there's a bit too much
> copy-and-paste going on, and I know some places where I could optimize
> the code generation a bit (mostly BPF_K type of instructions, dealing
> with immediates).
>
> From a features perspective, two things are missing:
>
> * tail calls
> * "far-branches", i.e. conditional branches that reach beyond 13b.
>
> The test_bpf.ko (only tested on 4.20!) passes all tests.
>
> I've done all the tests on QEMU (version 3.1.50), so no real hardware.
>
> Some questions/observations:
>
> * I've added "HAVE_EFFICIENT_UNALIGNED_ACCESS" to
> arch/riscv/Kconfig. Is this assumption correct?
>
> * emit_imm() just relies on lui, adds and shifts. No fancy xori cost
> optimizations like GCC does.
>
> * Suggestions on how to implement the tail call, given that the
> prologue/epilogue has variable size. I will dig into the details of
> mips/arm64/x86. :-)
>
> Next steps (prior patch proper) is cleaning up the code, add tail
> calls, and making sure that bpftool disassembly works correctly.
>
> All input are welcome. This is my first RISC-V hack, so I sure there
> are a lot things to improve!
>
>
> Thanks,
> Björn
>
>
> Björn Töpel (3):
> riscv: set HAVE_EFFICIENT_UNALIGNED_ACCESS
> riscv: add build infra for JIT compiler
> bpf, riscv: added eBPF JIT for RV64G
>
> arch/riscv/Kconfig | 2 +
> arch/riscv/Makefile | 4 +
> arch/riscv/net/Makefile | 5 +
> arch/riscv/net/bpf_jit_comp.c | 1612 +++++++++++++++++++++++++++++++++
> 4 files changed, 1623 insertions(+)
> create mode 100644 arch/riscv/net/Makefile
> create mode 100644 arch/riscv/net/bpf_jit_comp.c
Thanks for doing this. I saw a few reviews go by and I'm behind on email, so
I'm going to drop this until a v2.
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prev parent reply other threads:[~2019-01-30 2:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-15 8:35 [RFC PATCH 0/3] RV64G eBPF JIT Björn Töpel
2019-01-15 8:35 ` [RFC PATCH 1/3] riscv: set HAVE_EFFICIENT_UNALIGNED_ACCESS Björn Töpel
2019-01-15 15:39 ` Christoph Hellwig
2019-01-15 16:06 ` Björn Töpel
2019-01-25 20:21 ` Palmer Dabbelt
2019-01-26 1:33 ` Jim Wilson
2019-01-29 2:43 ` Palmer Dabbelt
2019-01-15 8:35 ` [RFC PATCH 2/3] riscv: add build infra for JIT compiler Björn Töpel
2019-01-15 15:43 ` Christoph Hellwig
2019-01-15 16:09 ` Björn Töpel
2019-01-15 8:35 ` [RFC PATCH 3/3] bpf, riscv: added eBPF JIT for RV64G Björn Töpel
2019-01-15 23:49 ` Daniel Borkmann
2019-01-16 7:23 ` Björn Töpel
2019-01-16 15:41 ` Daniel Borkmann
2019-01-16 19:06 ` Björn Töpel
2019-01-15 15:40 ` [RFC PATCH 0/3] RV64G eBPF JIT Christoph Hellwig
2019-01-15 16:03 ` Björn Töpel
2019-01-25 19:02 ` Palmer Dabbelt
2019-01-25 19:54 ` Paul Walmsley
2019-01-27 12:28 ` Björn Töpel
2019-01-30 2:02 ` Palmer Dabbelt [this message]
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