linux-kernel - Re: [PATCH v2 0/8] Implement EBPF on powerpc32

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Date:   Mon, 22 Mar 2021 10:53:23 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>, naveen.n.rao@...ux.ibm.com,
        sandipan@...ux.ibm.com, open list <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, Networking <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH v2 0/8] Implement EBPF on powerpc32

On Mon, Mar 22, 2021 at 9:37 AM Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
> This series implements extended BPF on powerpc32. For the implementation
> details, see the patch before the last.
>
> The following operations are not implemented:
>
>                 case BPF_ALU64 | BPF_DIV | BPF_X: /* dst /= src */
>                 case BPF_ALU64 | BPF_MOD | BPF_X: /* dst %= src */
>                 case BPF_STX | BPF_XADD | BPF_DW: /* *(u64 *)(dst + off) += src */
>
> The following operations are only implemented for power of two constants:
>
>                 case BPF_ALU64 | BPF_MOD | BPF_K: /* dst %= imm */
>                 case BPF_ALU64 | BPF_DIV | BPF_K: /* dst /= imm */
>
> Below are the results on a powerpc 885:
> - with the patch, with and without bpf_jit_enable
> - without the patch, with bpf_jit_enable (ie with CBPF)
>
> With the patch, with bpf_jit_enable = 1 :
>
> [   60.826529] test_bpf: Summary: 378 PASSED, 0 FAILED, [354/366 JIT'ed]
> [   60.832505] test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED
>
> With the patch, with bpf_jit_enable = 0 :
>
> [   75.186337] test_bpf: Summary: 378 PASSED, 0 FAILED, [0/366 JIT'ed]
> [   75.192325] test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED
>
> Without the patch, with bpf_jit_enable = 1 :
>
> [  186.112429] test_bpf: Summary: 371 PASSED, 7 FAILED, [119/366 JIT'ed]
>
> Couldn't run test_progs because it doesn't build (clang 11 crashes during the build).

Can you please try checking out the latest clang from sources and use
that one instead?

>
> Changes in v2:
> - Simplify 16 bits swap
> - Rework tailcall, use stack for tailcall counter
> - Fix handling of BPF_REG_FP:
>   - must be handler like any other register allthough only the lower 32 bits part is used as a pointer.
>   - r18 was TMP_REG, r17/r18 become de BPF_REG_FP
>   - r31 was BPF_REG_FP, it is now TMP_REG
> - removed bpf_jit32.h
> - Reorder register allocation dynamically to use the volatile registers as much as possible when not doing function calls (last patch - new)
>
> Christophe Leroy (8):
>   powerpc/bpf: Remove classical BPF support for PPC32
>   powerpc/bpf: Change register numbering for bpf_set/is_seen_register()
>   powerpc/bpf: Move common helpers into bpf_jit.h
>   powerpc/bpf: Move common functions into bpf_jit_comp.c
>   powerpc/bpf: Change values of SEEN_ flags
>   powerpc/asm: Add some opcodes in asm/ppc-opcode.h for PPC32 eBPF
>   powerpc/bpf: Implement extended BPF on PPC32
>   powerpc/bpf: Reallocate BPF registers to volatile registers when
>     possible on PPC32
>
>  Documentation/admin-guide/sysctl/net.rst |    2 +-
>  arch/powerpc/Kconfig                     |    3 +-
>  arch/powerpc/include/asm/ppc-opcode.h    |   12 +
>  arch/powerpc/net/Makefile                |    6 +-
>  arch/powerpc/net/bpf_jit.h               |   61 ++
>  arch/powerpc/net/bpf_jit32.h             |  139 ---
>  arch/powerpc/net/bpf_jit64.h             |   21 +-
>  arch/powerpc/net/bpf_jit_asm.S           |  226 -----
>  arch/powerpc/net/bpf_jit_comp.c          |  782 ++++-----------
>  arch/powerpc/net/bpf_jit_comp32.c        | 1095 ++++++++++++++++++++++
>  arch/powerpc/net/bpf_jit_comp64.c        |  295 +-----
>  11 files changed, 1372 insertions(+), 1270 deletions(-)
>  delete mode 100644 arch/powerpc/net/bpf_jit32.h
>  delete mode 100644 arch/powerpc/net/bpf_jit_asm.S
>  create mode 100644 arch/powerpc/net/bpf_jit_comp32.c
>
> --
> 2.25.0
>