linux-kernel - Re: [PATCH] arch/x86: reset MXCSR to default in kernel_fpu

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Date:   Thu, 11 Jun 2020 10:36:08 +0300
From:   Petteri Aimonen <jpa@....mail.kapsi.fi>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Borislav Petkov <bp@...en8.de>, Shuah Khan <shuah@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86-ml <x86@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arch/x86: reset MXCSR to default in kernel_fpu_begin()

Hi,

> How about putting the file you frob in
> /sys/kernel/debug/selftest_helpers/something_or_other.  The idea would
> be that /sys/kernel/debug/selftest_helpers would be a general place
> for kernel helpers needed to make selftests work.

Seems like this is the consensus for now.

Any opinions on whether the module should remove "selftest_helpers"
directory on unloading, or not?

1) Removing would break if other test modules will use the same dir.
2) Not removing will leave the directory dangling.
3) Remove only if empty is one option, though I'm unsure how to
   cleanly check if debugfs directory is empty.
4) E.g. /sys/kernel/debug/x86/ is created centrally and a symbol is
   exported for its dentry. But I'm not sure if it really makes sense
   to add another exported symbol just for selftest_helpers.

--
Petteri