Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Fri, 4 Feb 2022 15:48:40 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Marco Elver <elver@google.com>
Cc:     Tony Luck <tony.luck@intel.com>, Jakub Kicinski <kuba@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/3] x86/mce: Fix more noinstr fun
Message-ID: <Yf08yMZZDCtYMBVX@zn.tnic>
References: <20220204083015.17317-1-bp@alien8.de>
 <CANpmjNOvf7z4BdPqrJH2iF0KnZmP58uUzSH0fFoc4VNg+2S=hw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <CANpmjNOvf7z4BdPqrJH2iF0KnZmP58uUzSH0fFoc4VNg+2S=hw@mail.gmail.com>
Precedence: bulk

On Fri, Feb 04, 2022 at 12:24:00PM +0100, Marco Elver wrote:
> I guess to solve noinstr "calling" something else the only solution is
> to make the other function noinstr as well, or __always_inline.
> 
> Have you considered making some of these other functions 'noinstr' as
> well? I guess __always_inline works, esp. if there's just 1 caller.
> And by the looks of it you're getting a net .text reduction, so

Yeah, I started doing that and the savings were the persuasive
argument.

Even more so if the function has one caller only and gets inlined,
normally. I guess it doesn't get inlined when there's KASAN
instrumentation or so but I haven't verified it fully why.

Because even for oneliners like v8086_mode() which should get inlined
trivially, the compiler ends up doing this constprop thing - I guess
some constants folding optimization thing... it probably doesn't even
matter so much whether oneliners get inlined in KASAN-enabled builds so
I guess we might just as well force-inline them for the other configs.

> Acked-by: Marco Elver <elver@google.com>

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette