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 S1752189AbdI2Pib (ORCPT <rfc822;w@1wt.eu>);
        Fri, 29 Sep 2017 11:38:31 -0400
Received: from mx1.redhat.com ([209.132.183.28]:40788 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751349AbdI2Pia (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 29 Sep 2017 11:38:30 -0400
DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6CC2F4E028
Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com
Authentication-Results: ext-mx09.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jpoimboe@redhat.com
Date: Fri, 29 Sep 2017 10:38:28 -0500
From: Josh Poimboeuf <jpoimboe@redhat.com>
To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: use register variable to get stack pointer value
Message-ID: <20170929153828.rtxwllhsjgiaeaos@treble>
References: <20170929141537.29167-1-aryabinin@virtuozzo.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20170929141537.29167-1-aryabinin@virtuozzo.com>
User-Agent: Mutt/1.6.0.1 (2016-04-01)
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 29 Sep 2017 15:38:30 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Sep 29, 2017 at 05:15:36PM +0300, Andrey Ryabinin wrote:
> Currently we use current_stack_pointer() function to get the value
> of the stack pointer register. Since commit f5caf621ee35
> ("x86/asm: Fix inline asm call constraints for Clang") we have stack
> register variable declared. It can be used instead of current_stack_pointer()
> function which allows to optimize away some excessive "mov %rsp, %<dst>"
> instructions:
> 
> -mov    %rsp,%rdx
> -sub    %rdx,%rax
> -cmp    $0x3fff,%rax
> -ja     ffffffff810722fd <ist_begin_non_atomic+0x2d>
> 
> +sub    %rsp,%rax
> +cmp    $0x3fff,%rax
> +ja     ffffffff810722fa <ist_begin_non_atomic+0x2a>
> 
> Remove current_stack_pointer(), rename __asm_call_sp to current_stack_pointer
> and use it instead of removed function.
> 
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

-- 
Josh