From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH] arm64: KVM: Save two instructions in __guest_enter() Date: Thu, 25 Aug 2016 15:31:22 +0200 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 Return-path: Content-Disposition: inline In-Reply-To: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Shanker Donthineni Cc: Marc Zyngier , linux-kernel , linux-arm-kernel , kvmarm , Paolo Bonzini , Will Deacon , Catalin Marinas , James Morse List-Id: kvmarm@lists.cs.columbia.edu 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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: christoffer.dall@linaro.org (Christoffer Dall) Date: Thu, 25 Aug 2016 15:31:22 +0200 Subject: [PATCH] arm64: KVM: Save two instructions in __guest_enter() In-Reply-To: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> References: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> Message-ID: <20160825133122.GA8016@lvm> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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