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From:   Andy Lutomirski <luto@amacapital.net>
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Subject: Re: [PATCH] arch/x86: reset MXCSR to default in kernel_fpu_begin()
Date:   Thu, 11 Jun 2020 07:19:53 -0700
Message-Id: <301D30B5-26F7-454B-8C0C-A5DFC73222CF@amacapital.net>
References: <20200611091822.GA30352@zn.tnic>
Cc:     Petteri Aimonen <jpa@git.mail.kapsi.fi>,
        Andy Lutomirski <luto@kernel.org>,
        Shuah Khan <shuah@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86-ml <x86@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>
In-Reply-To: <20200611091822.GA30352@zn.tnic>
To:     Borislav Petkov <bp@alien8.de>
Sender: linux-kernel-owner@vger.kernel.org
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> On Jun 11, 2020, at 2:18 AM, Borislav Petkov <bp@alien8.de> wrote:
>=20
> =EF=BB=BFOn Thu, Jun 11, 2020 at 10:36:08AM +0300, Petteri Aimonen wrote:
>> Hi,
>>=20
>>> 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.
>>=20
>> Seems like this is the consensus for now.
>>=20
>> Any opinions on whether the module should remove "selftest_helpers"
>> directory on unloading, or not?
>>=20
>> 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.
>=20
> I'd say you do the simple thing and cleanup after you're done, i.e.,
> remove the dir. When something else starts using it, then it would need
> to be taught to deal with multiple users.

Seems good to me. Let=E2=80=99s have at least two users before we go nuts wi=
th the architecture :)

>=20
> Thx.
>=20
> --=20
> Regards/Gruss,
>    Boris.
>=20
> https://people.kernel.org/tglx/notes-about-netiquette