From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933895AbcHYNbZ (ORCPT ); Thu, 25 Aug 2016 09:31:25 -0400 Received: from mail-qt0-f182.google.com ([209.85.216.182]:33274 "EHLO mail-qt0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754441AbcHYNbY (ORCPT ); Thu, 25 Aug 2016 09:31:24 -0400 Date: Thu, 25 Aug 2016 15:31:22 +0200 From: Christoffer Dall To: Shanker Donthineni Cc: Marc Zyngier , linux-kernel , linux-arm-kernel , kvmarm , Paolo Bonzini , Will Deacon , Catalin Marinas , James Morse Subject: Re: [PATCH] arm64: KVM: Save two instructions in __guest_enter() Message-ID: <20160825133122.GA8016@lvm> References: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Shanker, On Tue, Aug 09, 2016 at 08:15:36PM -0500, Shanker Donthineni wrote: > We are doing an unnecessary stack push/pop operation when restoring > the guest registers x0-x18 in __guest_enter(). This patch saves the > two instructions by using x18 as a base register. No need to store > the vcpu context pointer in stack because it is redundant and not > being used anywhere, the same information is available in tpidr_el2. Does this have any measureable benefit? Thanks, -Christoffer