From mboxrd@z Thu Jan 1 00:00:00 1970 From: shankerd@codeaurora.org (Shanker Donthineni) Date: Mon, 29 Aug 2016 10:22:06 -0500 Subject: [PATCH] arm64: KVM: Save two instructions in __guest_enter() In-Reply-To: <20160825133122.GA8016@lvm> References: <1470791736-13949-1-git-send-email-shankerd@codeaurora.org> <20160825133122.GA8016@lvm> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Christoffer, This is change may not provide the measurable performance improvement, but still we can save a few cpu cycles on vCPU context switch and also improves the code readability. On 08/25/2016 08:31 AM, Christoffer Dall wrote: > 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 -- Shanker Donthineni Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.