linux-kernel - Re: x86/paravirt: Use a single ops structure

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Message-ID: <CAB9dFdtLHkpZqrmNEuMfPdOmZm32q5SXYx1zMexSd94rt3KyDw@mail.gmail.com>
Date:   Mon, 29 Oct 2018 09:58:28 -0300
From:   Marc Dionne <marc.dionne@...istor.com>
To:     jgross@...e.com
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: x86/paravirt: Use a single ops structure

On Tue, Oct 23, 2018 at 2:37 PM Linux Kernel Mailing List
<linux-kernel@...r.kernel.org> wrote:
>
> Commit:     5c83511bdb9832c86be20fb86b783356e2f58062
> Parent:     27876f3882fdd4acb3d3614a0133ecdc777fc292
> Refname:    refs/heads/master
> Web:        https://git.kernel.org/torvalds/c/5c83511bdb9832c86be20fb86b783356e2f58062
> Author:     Juergen Gross <jgross@...e.com>
> AuthorDate: Tue Aug 28 09:40:19 2018 +0200
> Committer:  Thomas Gleixner <tglx@...utronix.de>
> CommitDate: Mon Sep 3 16:50:35 2018 +0200
>
>     x86/paravirt: Use a single ops structure
>
>     Instead of using six globally visible paravirt ops structures combine
>     them in a single structure, keeping the original structures as
>     sub-structures.
>
>     This avoids the need to assemble struct paravirt_patch_template at
>     runtime on the stack each time apply_paravirt() is being called (i.e.
>     when loading a module).

The above commit replaces pv_lock_ops, which was EXPORT_SYMBOL, with
something that is part of pv_ops, which is EXPORT_SYMBOL_GPL.    When
CONFIG_PARAVIRT_SPINLOCKS is set, this has the side effect of making
spin_lock() unusable by out of tree modules, which will likely be an
issue for many, if not most of them.

Marc