netdev - Re: [PATCH bpf-next v2 0/4] Add RISC-V (RV64G) BPF JIT

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Date:   Tue, 5 Feb 2019 17:05:46 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     bjorn.topel@...il.com, linux-riscv@...ts.infradead.org,
        ast@...nel.org, netdev@...r.kernel.org
Cc:     palmer@...ive.com, hch@...radead.org
Subject: Re: [PATCH bpf-next v2 0/4] Add RISC-V (RV64G) BPF JIT

On 02/05/2019 01:41 PM, bjorn.topel@...il.com wrote:
> From: Björn Töpel <bjorn.topel@...il.com>
> 
> Hi!
> 
> This v2 series adds an RV64G BPF JIT to the kernel.
> 
> At the moment the RISC-V Linux port does not support
> CONFIG_HAVE_KPROBES (Patrick Stählin sent out an RFC last year), which
> means that CONFIG_BPF_EVENTS is not supported. Thus, no tests
> involving BPF_PROG_TYPE_TRACEPOINT, BPF_PROG_TYPE_PERF_EVENT,
> BPF_PROG_TYPE_KPROBE and BPF_PROG_TYPE_RAW_TRACEPOINT passes.
> 
> The implementation does not support "far branching" (>4KiB).
> 
> Test results:
>   # modprobe test_bpf
>   test_bpf: Summary: 378 PASSED, 0 FAILED, [366/366 JIT'ed]
> 
>   # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
>   # ./test_verifier
>   ...
>   Summary: 761 PASSED, 507 SKIPPED, 2 FAILED
> 
> Note that "test_verifier" was run with one build with
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y and one without, otherwise
> many of the the tests that require unaligned access were skipped.
> 
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y:
>   # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
>   # ./test_verifier | grep -c 'NOTE.*unknown align'
>   0
> 
> No CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS:
>   # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
>   # ./test_verifier | grep -c 'NOTE.*unknown align'
>   59
> 
> The two failing test_verifier tests are:
>   "ld_abs: vlan + abs, test 1"
>   "ld_abs: jump around ld_abs"
> 
> This is due to that "far branching" involved in those tests.
> All tests where done on QEMU emulator version 3.1.50
> (v3.1.0-688-g8ae951fbc106). I'll test it on real hardware, when I get
> access to it.
> 
> I'm routing this patch via bpf-next/netdev mailing list (after a
> conversation with Palmer at FOSDEM), mainly because the other JITs
> went that path.
> 
> Again, thanks for all the comments!
> 
> Cheers,
> Björn
> 
> v1 -> v2:
> * Added JMP32 support. (Daniel)
> * Add RISC-V to Documentation/sysctl/net.txt. (Daniel)
> * Fixed seen_call() asymmetry. (Daniel)
> * Fixed broken bpf_flush_icache() range. (Daniel)
> * Added alignment annotations to some selftests.
> 
> RFCv1 -> v1:
> * Cleaned up the Kconfig and net/Makefile. (Christoph)
> * Removed the entry-stub and squashed the build/config changes to be
>   part of the JIT implementation. (Christoph)
> * Simplified the register tracking code. (Daniel)
> * Removed unused macros. (Daniel)
> * Added myself as maintainer and updated documentation. (Daniel)
> * Removed HAVE_EFFICIENT_UNALIGNED_ACCESS. (Christoph, Palmer)
> * Added tail-calls and cleaned up the code.
> 
> 
> Björn Töpel (4):
>   bpf, riscv: add BPF JIT for RV64G
>   MAINTAINERS: add RISC-V BPF JIT maintainer
>   bpf, doc: add RISC-V JIT to BPF documentation
>   selftests/bpf: add "any alignment" annotation for some tests
> 
>  Documentation/networking/filter.txt           |   16 +-
>  Documentation/sysctl/net.txt                  |    1 +
>  MAINTAINERS                                   |    6 +
>  arch/riscv/Kconfig                            |    1 +
>  arch/riscv/Makefile                           |    2 +-
>  arch/riscv/net/Makefile                       |    1 +
>  arch/riscv/net/bpf_jit_comp.c                 | 1602 +++++++++++++++++
>  .../selftests/bpf/verifier/ctx_sk_msg.c       |    1 +
>  .../testing/selftests/bpf/verifier/ctx_skb.c  |    1 +
>  tools/testing/selftests/bpf/verifier/jmp32.c  |   22 +
>  tools/testing/selftests/bpf/verifier/jset.c   |    2 +
>  .../selftests/bpf/verifier/spill_fill.c       |    1 +
>  .../selftests/bpf/verifier/spin_lock.c        |    2 +
>  .../selftests/bpf/verifier/value_ptr_arith.c  |    4 +
>  14 files changed, 1654 insertions(+), 8 deletions(-)
>  create mode 100644 arch/riscv/net/Makefile
>  create mode 100644 arch/riscv/net/bpf_jit_comp.c

Applied, thanks!