From: Daniel Borkmann <daniel@iogearbox.net>
To: Yonghong Song <yhs@fb.com>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@fb.com>, kernel-team@fb.com
Subject: Re: [PATCH bpf-next] selftests/bpf: change llvm flag -mcpu=probe to -mcpu=v3
Date: Wed, 19 Feb 2020 17:56:36 +0100 [thread overview]
Message-ID: <956ccea3-0440-7c59-9c75-90cd7b25afb7@iogearbox.net> (raw)
In-Reply-To: <20200219004236.2291125-1-yhs@fb.com>
On 2/19/20 1:42 AM, Yonghong Song wrote:
> The latest llvm supports cpu version v3, which is cpu version v1
> plus some additional 64bit jmp insns and 32bit jmp insn support.
>
> In selftests/bpf Makefile, the llvm flag -mcpu=probe did runtime
> probe into the host system. Depending on compilation environments,
> it is possible that runtime probe may fail, e.g., due to
> memlock issue. This will cause generated code with cpu version v1.
But those are tiny BPF progs that LLVM is probing. If memlock is not
sufficient, should it try to bump the limit with the diff needed and
only if that fails as well then it bails out to v1.
> This may cause confusion as the same compiler and the same C code
> generates different byte codes in different environment.
>
> Let us change the llvm flag -mcpu=probe to -mcpu=v3 so the
> generated code will be the same regardless of the compilation
> environment.
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
next prev parent reply other threads:[~2020-02-19 16:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 0:42 [PATCH bpf-next] selftests/bpf: change llvm flag -mcpu=probe to -mcpu=v3 Yonghong Song
2020-02-19 7:34 ` Andrii Nakryiko
2020-02-19 16:56 ` Daniel Borkmann [this message]
2020-02-19 17:04 ` Yonghong Song
2020-02-19 17:06 ` Alexei Starovoitov
2020-02-19 23:17 ` Alexei Starovoitov
2020-02-20 0:15 ` Daniel Borkmann
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