linux-kernel - Re: [PATCH v2] x86/cpufeature: guard asm_volatile_goto usage with NO_BPF

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Message-ID: <20180420081936.GD4064@hirez.programming.kicks-ass.net>
Date:   Fri, 20 Apr 2018 10:19:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yonghong Song <yhs@...com>
Cc:     mingo@...nel.org, ast@...com, daniel@...earbox.net,
        linux-kernel@...r.kernel.org, x86@...nel.org, kernel-team@...com
Subject: Re: [PATCH v2] x86/cpufeature: guard asm_volatile_goto usage with
 NO_BPF_WORKAROUND

On Sat, Apr 14, 2018 at 09:27:38PM -0700, Yonghong Song wrote:

> This patch adds a preprocessor guard NO_BPF_WORKAROUND around the
> asm_volatile_goto based static_cpu_has(). NO_BPF_WORKAROUND is set
> at toplevel Makefile when compiler supports asm-goto. That is,
> if the compiler supports asm-goto, the kernel build will use
> asm-goto version of static_cpu_has().

Hurm, so adding __BPF__ for BPF compiles isn't an option? It seems to me
having a CPP flag to identify BPF compile context might be useful in
general.