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

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Message-ID: <20200603051946.GF17423@lakka.kapsi.fi>
Date:   Wed, 3 Jun 2020 08:19:46 +0300
From:   Petteri Aimonen <jpa@....mail.kapsi.fi>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        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,

> Is it correct to assume the stuff checked differs from test to test
> and done in user-space.
> 
> > undo_evil_state();
> 
> Is it correct to assume undoing evil differs from test to test
> and done in user-space, provide it can be done from userspace.

Yes, currently the test works like:

do_test_setup();
read_from_debugfs_file();
check_results();

and the middle step stays the same. But of course in general case there 
could be argument passing etc, even though the test for this issue 
doesn't need them.

Myself I don't see the problem with just adding a file under debugfs and 
bind to its read.

--
Petteri