From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mario Smarduch Subject: Re: [PATCH 0/3] arm: KVM: VFP lazy switch in KVM Host Mode may save upto 98% Date: Sun, 28 Jun 2015 10:57:09 -0700 Message-ID: <55903575.8060702@samsung.com> References: <1435203028-23142-1-git-send-email-m.smarduch@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id A12C756BB5 for ; Sun, 28 Jun 2015 13:46:22 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id i8esVDSJXRY6 for ; Sun, 28 Jun 2015 13:46:20 -0400 (EDT) Received: from usmailout4.samsung.com (mailout4.w2.samsung.com [211.189.100.14]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id C6B0C56BA8 for ; Sun, 28 Jun 2015 13:46:20 -0400 (EDT) Received: from uscpsbgex3.samsung.com (u124.gpu85.samsung.co.kr [203.254.195.124]) by usmailout4.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NQO00GY11VR1A10@usmailout4.samsung.com> for kvmarm@lists.cs.columbia.edu; Sun, 28 Jun 2015 13:57:27 -0400 (EDT) In-reply-to: <1435203028-23142-1-git-send-email-m.smarduch@samsung.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com, christoffer.dall@linaro.org Cc: pbonzini@redhat.com, will.deacon@arm.com, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com List-Id: kvmarm@lists.cs.columbia.edu Hi Marc, Christoffer - to clarify - this series may be causing a conflict with the arm64 basic approach, and arm32 exit code touch ups. The intent for this series is more of an RFC or preview, to get some feedback - if this approach is sensible (I guess later applied to arm64 as well if it is). Thanks, - Mario On 06/24/2015 08:30 PM, Mario Smarduch wrote: > Currently we do a lazy VFP switch in Hyp mode, but once we exit and re-enter hyp > mode we trap again on VFP access. This mode has shown around 30-50% improvement > running hackbench and lmbench. > > This patch series extends lazy VFP switch beyond Hyp mode to KVM host mode. > > 1 - On guest access we switch from host to guest and set a flag accessible to > host > 2 - On exit to KVM host, VFP state is restored on vcpu_put if flag is marked (1) > 3 - Otherwise guest is resumed and continues to use its VFP registers. > 4 - In case of 2 on VM entry we set VFP trap flag to repeat 1. > > If guest does not access VFP registers them implemenation remains the same. > > Executing hackbench on Fast Models and Exynos arm32 board shows good > results. Considering all exits 2% of the time KVM host lazy vfp switch is > invoked. > > Howeverr this patch set requires more burn in time and testing under various > loads. > > Currently ARM32 is addressed later ARM64. > > Mario Smarduch (3): > define headers and offsets to mange VFP state > Implement lazy VFP switching outside of Hyp Mode > Add VFP lazy switch hooks in Host KVM > > arch/arm/include/asm/kvm_asm.h | 1 + > arch/arm/include/asm/kvm_host.h | 3 +++ > arch/arm/kernel/asm-offsets.c | 1 + > arch/arm/kvm/arm.c | 15 ++++++++++++ > arch/arm/kvm/interrupts.S | 49 +++++++++++++++++++++++++-------------- > 5 files changed, 51 insertions(+), 18 deletions(-) >