From: Yonghong Song <yhs@fb.com>
To: Brendan Jackman <jackmanb@google.com>, <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
KP Singh <kpsingh@chromium.org>,
Florent Revest <revest@chromium.org>,
<linux-kernel@vger.kernel.org>, Jann Horn <jannh@google.com>
Subject: Re: [PATCH bpf-next v3 09/14] bpf: Pull out a macro for interpreting atomic ALU operations
Date: Thu, 3 Dec 2020 22:30:18 -0800 [thread overview]
Message-ID: <f1d5ec7e-6231-0876-f25d-9dd5da4112d0@fb.com> (raw)
In-Reply-To: <20201203160245.1014867-10-jackmanb@google.com>
On 12/3/20 8:02 AM, Brendan Jackman wrote:
> Since the atomic operations that are added in subsequent commits are
> all isomorphic with BPF_ADD, pull out a macro to avoid the
> interpreter becoming dominated by lines of atomic-related code.
>
> Note that this sacrificies interpreter performance (combining
> STX_ATOMIC_W and STX_ATOMIC_DW into single switch case means that we
> need an extra conditional branch to differentiate them) in favour of
> compact and (relatively!) simple C code.
>
> Change-Id: I8cae5b66e75f34393de6063b91c05a8006fdd9e6
> Signed-off-by: Brendan Jackman <jackmanb@google.com>
Ack with a minor suggestion below.
Acked-by: Yonghong Song <yhs@fb.com>
> ---
> kernel/bpf/core.c | 79 +++++++++++++++++++++++------------------------
> 1 file changed, 38 insertions(+), 41 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 28f960bc2e30..498d3f067be7 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -1618,55 +1618,52 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u64 *stack)
> LDX_PROBE(DW, 8)
> #undef LDX_PROBE
>
> - STX_ATOMIC_W:
> - switch (IMM) {
> - case BPF_ADD:
> - /* lock xadd *(u32 *)(dst_reg + off16) += src_reg */
> - atomic_add((u32) SRC, (atomic_t *)(unsigned long)
> - (DST + insn->off));
> - break;
> - case BPF_ADD | BPF_FETCH:
> - SRC = (u32) atomic_fetch_add(
> - (u32) SRC,
> - (atomic_t *)(unsigned long) (DST + insn->off));
> - break;
> - case BPF_XCHG:
> - SRC = (u32) atomic_xchg(
> - (atomic_t *)(unsigned long) (DST + insn->off),
> - (u32) SRC);
> - break;
> - case BPF_CMPXCHG:
> - BPF_R0 = (u32) atomic_cmpxchg(
> - (atomic_t *)(unsigned long) (DST + insn->off),
> - (u32) BPF_R0, (u32) SRC);
> +#define ATOMIC(BOP, KOP) \
ATOMIC a little bit generic. Maybe ATOMIC_FETCH_BOP?
> + case BOP: \
> + if (BPF_SIZE(insn->code) == BPF_W) \
> + atomic_##KOP((u32) SRC, (atomic_t *)(unsigned long) \
> + (DST + insn->off)); \
> + else \
> + atomic64_##KOP((u64) SRC, (atomic64_t *)(unsigned long) \
> + (DST + insn->off)); \
> + break; \
> + case BOP | BPF_FETCH: \
> + if (BPF_SIZE(insn->code) == BPF_W) \
> + SRC = (u32) atomic_fetch_##KOP( \
> + (u32) SRC, \
> + (atomic_t *)(unsigned long) (DST + insn->off)); \
> + else \
> + SRC = (u64) atomic64_fetch_##KOP( \
> + (u64) SRC, \
> + (atomic64_t *)(s64) (DST + insn->off)); \
> break;
> - default:
> - goto default_label;
> - }
> - CONT;
>
> STX_ATOMIC_DW:
> + STX_ATOMIC_W:
> switch (IMM) {
> - case BPF_ADD:
> - /* lock xadd *(u64 *)(dst_reg + off16) += src_reg */
> - atomic64_add((u64) SRC, (atomic64_t *)(unsigned long)
> - (DST + insn->off));
> - break;
> - case BPF_ADD | BPF_FETCH:
> - SRC = (u64) atomic64_fetch_add(
> - (u64) SRC,
> - (atomic64_t *)(s64) (DST + insn->off));
> - break;
> + ATOMIC(BPF_ADD, add)
> +
> case BPF_XCHG:
> - SRC = (u64) atomic64_xchg(
> - (atomic64_t *)(u64) (DST + insn->off),
> - (u64) SRC);
> + if (BPF_SIZE(insn->code) == BPF_W)
> + SRC = (u32) atomic_xchg(
> + (atomic_t *)(unsigned long) (DST + insn->off),
> + (u32) SRC);
> + else
> + SRC = (u64) atomic64_xchg(
> + (atomic64_t *)(u64) (DST + insn->off),
> + (u64) SRC);
> break;
> case BPF_CMPXCHG:
> - BPF_R0 = (u64) atomic64_cmpxchg(
> - (atomic64_t *)(u64) (DST + insn->off),
> - (u64) BPF_R0, (u64) SRC);
> + if (BPF_SIZE(insn->code) == BPF_W)
> + BPF_R0 = (u32) atomic_cmpxchg(
> + (atomic_t *)(unsigned long) (DST + insn->off),
> + (u32) BPF_R0, (u32) SRC);
> + else
> + BPF_R0 = (u64) atomic64_cmpxchg(
> + (atomic64_t *)(u64) (DST + insn->off),
> + (u64) BPF_R0, (u64) SRC);
> break;
> +
> default:
> goto default_label;
> }
>
next prev parent reply other threads:[~2020-12-04 6:31 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 16:02 [PATCH bpf-next v3 00/14] Atomics for eBPF Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 01/14] bpf: x86: Factor out emission of ModR/M for *(reg + off) Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 02/14] bpf: x86: Factor out emission of REX byte Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 03/14] bpf: x86: Factor out function to emit NEG Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 04/14] bpf: x86: Factor out a lookup table for some ALU opcodes Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 05/14] bpf: Rename BPF_XADD and prepare to encode other atomics in .imm Brendan Jackman
2020-12-04 4:49 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 06/14] bpf: Move BPF_STX reserved field check into BPF_STX verifier code Brendan Jackman
2020-12-04 4:51 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 07/14] bpf: Add BPF_FETCH field / create atomic_fetch_add instruction Brendan Jackman
2020-12-04 5:02 ` Yonghong Song
2020-12-04 5:27 ` Yonghong Song
2020-12-04 9:12 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 08/14] bpf: Add instructions for atomic_[cmp]xchg Brendan Jackman
2020-12-04 5:34 ` Yonghong Song
2020-12-04 9:26 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 09/14] bpf: Pull out a macro for interpreting atomic ALU operations Brendan Jackman
2020-12-04 6:30 ` Yonghong Song [this message]
2020-12-04 9:29 ` Brendan Jackman
2020-12-04 15:20 ` Yonghong Song
2020-12-03 16:02 ` [PATCH bpf-next v3 10/14] bpf: Add bitwise atomic instructions Brendan Jackman
2020-12-04 6:42 ` Yonghong Song
2020-12-04 9:36 ` Brendan Jackman
2020-12-04 15:21 ` Yonghong Song
2020-12-07 11:28 ` Brendan Jackman
2020-12-07 15:58 ` Yonghong Song
2020-12-07 16:14 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 11/14] tools build: Implement feature check for BPF atomics in Clang Brendan Jackman
2020-12-03 21:02 ` Andrii Nakryiko
2020-12-03 16:02 ` [PATCH bpf-next v3 12/14] bpf: Pull tools/build/feature biz into selftests Makefile Brendan Jackman
2020-12-03 21:01 ` Andrii Nakryiko
2020-12-04 9:41 ` Brendan Jackman
2020-12-04 19:00 ` Andrii Nakryiko
2020-12-07 11:00 ` Brendan Jackman
2020-12-08 2:19 ` Andrii Nakryiko
2020-12-08 17:04 ` Brendan Jackman
2020-12-08 18:31 ` Andrii Nakryiko
2020-12-03 16:02 ` [PATCH bpf-next v3 13/14] bpf: Add tests for new BPF atomic operations Brendan Jackman
2020-12-04 7:06 ` Yonghong Song
2020-12-04 9:45 ` Brendan Jackman
2020-12-04 15:28 ` Yonghong Song
2020-12-04 19:49 ` Andrii Nakryiko
2020-12-07 15:48 ` Brendan Jackman
2020-12-03 16:02 ` [PATCH bpf-next v3 14/14] bpf: Document new atomic instructions Brendan Jackman
2020-12-03 16:10 ` [PATCH bpf-next v3 00/14] Atomics for eBPF Brendan Jackman
2020-12-04 4:46 ` Yonghong Song
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