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

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Message-ID: <f5f80b20-c8e8-4f75-c5b2-dbd7ce56ca41@linuxfoundation.org>
Date:   Thu, 11 Jun 2020 08:38:18 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Petteri Aimonen <jpa@....mail.kapsi.fi>
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>,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] arch/x86: reset MXCSR to default in kernel_fpu_begin()

On 6/2/20 11:19 PM, Petteri Aimonen wrote:
> 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();
> 

You will need a 4th clanup step step of undo_test_setup().

> 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.
> 

thanks,
-- Shuah