Re: [PATCH bpf-next 2/5] riscv, bpf: Relax restrictions on Zbb instructions

From: Conor Dooley <conor@kernel.org>
To: Pu Lehui <pulehui@huaweicloud.com>
Cc: "Björn Töpel" <bjorn@kernel.org>,
	"Stefan O'Rear" <sorear@fastmail.com>,
	bpf@vger.kernel.org, linux-riscv@lists.infradead.org,
	netdev@vger.kernel.org, "Alexei Starovoitov" <ast@kernel.org>,
	"Daniel Borkmann" <daniel@iogearbox.net>,
	"Andrii Nakryiko" <andrii@kernel.org>,
	"Martin KaFai Lau" <martin.lau@linux.dev>,
	"Eduard Zingerman" <eddyz87@gmail.com>,
	"Song Liu" <song@kernel.org>, "Yonghong Song" <yhs@fb.com>,
	"John Fastabend" <john.fastabend@gmail.com>,
	"KP Singh" <kpsingh@kernel.org>,
	"Stanislav Fomichev" <sdf@google.com>,
	"Hao Luo" <haoluo@google.com>, "Jiri Olsa" <jolsa@kernel.org>,
	"Mykola Lysenko" <mykolal@fb.com>,
	"Manu Bretelle" <chantr4@gmail.com>,
	"Pu Lehui" <pulehui@huawei.com>
Subject: Re: [PATCH bpf-next 2/5] riscv, bpf: Relax restrictions on Zbb instructions
Date: Wed, 3 Apr 2024 13:29:49 +0100	[thread overview]
Message-ID: <20240403-clanking-undress-b18346aa4cef@spud> (raw)
In-Reply-To: <d6eae62b-60fd-4f3c-92e4-7ea5f1c4fc68@huaweicloud.com>

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On Wed, Apr 03, 2024 at 06:05:38PM +0800, Pu Lehui wrote:
> Hi Conor and Björn,
> 
> Thanks for your explanation. I totally agree with what you said,
> "CONFIG_RISCV_ISA_ZBB only controls whether optimizations for Zbb are built
> so that if Zbb is detected they can be used.".
> 
> Since the instructions emited by bpf jit are in kernel space, they should
> indeed be aligned in this regard.
> 
> PS: It's a bit difficult to understand this,😅 if I'm wrong please don't
> hesitate to tell me.

I think your understanding is correct. Sorry if I confused you at all!

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