linux-kernel - RE: [PATCH V2 01/15] x86/fsgsbase/64: Introduce FS/GS base helper functions

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Message-ID: <C9BB696F3A938947B10DCAD29FAB8FFA66BB9450@CRSMSX101.amr.corp.intel.com>
Date:   Thu, 31 May 2018 21:03:00 +0000
From:   "Bae, Chang Seok" <chang.seok.bae@...el.com>
To:     Andy Lutomirski <luto@...nel.org>
CC:     "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Metzger, Markus T" <markus.t.metzger@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH V2 01/15] x86/fsgsbase/64: Introduce FS/GS base helper
 functions

>> Notion of "active" and "inactive" are used to distinguish
>> GS bases between "kernel" and "user". "inactive" GS base
>> is the GS base, backed up at kernel entries, of inactive
>> (user) task's.

> I'm fine with the code, but the changelog entry is confusing.  A bunch
> of the active helpers don't contain the term "active".

Okay, will take "active" out from the note.

>> +/*
>> + * Read/write an (inactive) task's fsbase or gsbase. This returns
>> + * the value that the FS/GS base would have (if the task were to be
>> + * resumed). The current task is also supported.
>> + */

> Please change to "Read/write a task's fsbase or gsbase. ... These work
> on current or on a different non-running task."

Will do that.

>> +
>> +unsigned long read_task_fsbase(struct task_struct *task)
>> +{
>> +       unsigned long fsbase;
>> +
>> +       if (task == current)
>> +               fsbase = read_fsbase();
>> +       else
>> +               /*
>> +                * XXX: This will not behave as expected if called
>> +                * if fsindex != 0
>> +                */
>> +               fsbase = task->thread.fsbase;
>> +

> Please put braces around the if and else blocks whenever either of
> them spans multiple lines.  Also, maybe change add a note to the
> comment and/or the changelog that this is preserving an existing bug
> and that it's fixed later in the series.

Okay, thanks.