From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753941AbdGLTY2 (ORCPT <rfc822;w@1wt.eu>);
        Wed, 12 Jul 2017 15:24:28 -0400
Received: from mail-wm0-f68.google.com ([74.125.82.68]:33012 "EHLO
        mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752363AbdGLTY0 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 12 Jul 2017 15:24:26 -0400
Date: Wed, 12 Jul 2017 21:24:22 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Lutomirski <luto@kernel.org>,
        Denys Vlasenko <dvlasenk@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Kalle Valo <kvalo@codeaurora.org>, Peter Anvin <hpa@zytor.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>, Arnd Bergmann <arnd@arndb.de>,
        Peter Zijlstra <peterz@infradead.org>, Brian Gerst <brgerst@gmail.com>,
        "linux-tip-commits@vger.kernel.org" 
        <linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/urgent] x86/io: Mark target address as output in
 'insb()' asm
Message-ID: <20170712192421.cpuucr2a233xcovl@gmail.com>
References: <20170710144425.2238584-1-arnd@arndb.de>
 <tip-ea1b2ee6eacc4413b1dfba566480c90d0da4ec81@git.kernel.org>
 <CA+55aFzrMBzQO4jDhaG2tbgWpFGqfK+-VXehG_tSCrFZTx4D5Q@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CA+55aFzrMBzQO4jDhaG2tbgWpFGqfK+-VXehG_tSCrFZTx4D5Q@mail.gmail.com>
User-Agent: NeoMutt/20170113 (1.7.2)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Wed, Jul 12, 2017 at 6:10 AM, tip-bot for Arnd Bergmann
> <tipbot@zytor.com> wrote:
> >
> > Apparently the assember constraints are slightly off here, as marking the
> > 'addr' argument as a memory output seems appropriate here and gets rid
> > of the warning. For consistency I'm also adding it as input for outsb().
> 
> The new constraints look very questionable to me.

Ok, I've removed the commit.

> The real fix is probably to just mark them as "clobbers memory" (ie
> just add "memory" to the clobber list).
> 
> If you want to be fancy, you can try to do what <asm/uaccess.h> does,
> which is a disgusting hack, but has traditionally worked;
> 
>   struct __large_struct { unsigned long buf[100]; };
>   #define __m(x) (*(struct __large_struct __user *)(x))
> 
> and then use your approach with "m" and "=m".

Arnd, could you please try Linus's suggestions?

Thanks,

	Ingo