linux-kernel - Re: [PATCH 6/7] modules: Add CONFIG_ARCH_WANTS_MODULES_DATA_IN

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Message-ID: <YfBnNuXpR2l2AuCP@bombadil.infradead.org>
Date:   Tue, 25 Jan 2022 13:10:14 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     Jessica Yu <jeyu@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "kgdb-bugreport@...ts.sourceforge.net" 
        <kgdb-bugreport@...ts.sourceforge.net>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 6/7] modules: Add
 CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC

On Mon, Jan 24, 2022 at 09:22:34AM +0000, Christophe Leroy wrote:
> This can also be useful on other powerpc/32 in order to maximize the
> chance of code being close enough to kernel core to avoid branch
> trampolines.

Curious about all this branch trampoline talk. Do you have data to show
negative impact with things as-is?

Also, was powerpc/32 broken then without this? The commit log seems to
suggest so, but I don't think that's the case. How was this issue noticed?

Are there other future CPU families being planned where this is all true for
as well? Are they goin to be 32-bit as well?

  Luis