linux-kernel - Re: [PATCH bpf-next v3 0/2] bpf,riscv: Add support for BPF Arena

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Date: Wed, 27 Mar 2024 13:23:58 +0100
From: Björn Töpel <bjorn@...nel.org>
To: Puranjay Mohan <puranjay12@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Luke Nelson <luke.r.nels@...il.com>, Xi Wang <xi.wang@...il.com>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>, bpf@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Pu Lehui <pulehui@...weicloud.com>
Subject: Re: [PATCH bpf-next v3 0/2] bpf,riscv: Add support for BPF Arena

On Tue, 26 Mar 2024 at 23:49, Puranjay Mohan <puranjay12@...il.com> wrote:
>
> Changes in V3
> V2: https://lore.kernel.org/bpf/20240325155434.65589-1-puranjay12@gmail.com/
> - Use REG_DONT_CLEAR_MARKER in place of DONT_CLEAR as the name.
> - Use RV_REG_ZERO for the above as it is guaranteed to be never used in as
>   dst/src register in BPF LDX/STX/ST instructions.
> - Use #define RV_REG_ARENA for RV_REG_S7
>
> Changes in V2
> V1: https://lore.kernel.org/bpf/20240323154652.54572-1-puranjay12@gmail.com/
> - Used S7 in place of S11 for storing the kernel_vm_start
> - Used 17 in place of 16 for DONT_CLEAR marker
> - Remove an unused variable
> - Removed some misleading information from the commit message.
>
> This series adds the support for PROBE_MEM32 and bpf_addr_space_cast
> instructions to the RISCV BPF JIT. These two instructions allow the
> enablement of BPF Arena.
>
> All arena related selftests are passing:
>
>   root@...tester:~/bpf# uname -p
>   riscv64
>   root@...tester:~/bpf# ./test_progs -a "*arena*"
>   #3/1     arena_htab/arena_htab_llvm:OK
>   #3/2     arena_htab/arena_htab_asm:OK
>   #3       arena_htab:OK
>   #4/1     arena_list/arena_list_1:OK
>   #4/2     arena_list/arena_list_1000:OK
>   #4       arena_list:OK
>   #434/1   verifier_arena/basic_alloc1:OK
>   #434/2   verifier_arena/basic_alloc2:OK
>   #434/3   verifier_arena/basic_alloc3:OK
>   #434/4   verifier_arena/iter_maps1:OK
>   #434/5   verifier_arena/iter_maps2:OK
>   #434/6   verifier_arena/iter_maps3:OK
>   #434     verifier_arena:OK
>   Summary: 3/10 PASSED, 0 SKIPPED, 0 FAILED
>
> This feature needs the following two fixes in the bpf/bpf.git to work
> properly:
>
> f7f5d1808b1b6 ("bpf: verifier: fix addr_space_cast from as(1) to as(0)")
> 443574b033876 ("riscv, bpf: Fix kfunc parameters incompatibility between bpf and riscv abi")
>
> There is a lot of code repetition for LDX, STX, and ST. I will be sending a
> follow-up patch to refactor these.

Thank you, and please address Lehui's remarks as well.

For the series:

Tested-by: Björn Töpel <bjorn@...osinc.com>
Acked-by: Björn Töpel <bjorn@...nel.org>