From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933507AbcIAOzY (ORCPT ); Thu, 1 Sep 2016 10:55:24 -0400 Received: from foss.arm.com ([217.140.101.70]:60924 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750841AbcIAOzX (ORCPT ); Thu, 1 Sep 2016 10:55:23 -0400 Date: Thu, 1 Sep 2016 15:55:25 +0100 From: Will Deacon To: Punit Agrawal Cc: kvm@vger.kernel.org, Marc Zyngier , linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [RFC PATCH 6/7] arm64: KVM: Handle trappable TLB instructions Message-ID: <20160901145525.GM6721@arm.com> References: <1471344312-26685-1-git-send-email-punit.agrawal@arm.com> <1471344312-26685-7-git-send-email-punit.agrawal@arm.com> <20160819151846.GE9893@arm.com> <87a8g2sb4o.fsf@e105922-lin.cambridge.arm.com> <87h9a7rhvf.fsf@e105922-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87h9a7rhvf.fsf@e105922-lin.cambridge.arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 26, 2016 at 10:37:08AM +0100, Punit Agrawal wrote: > > Will Deacon writes: > >> The easiest thing to do is just TLBI VMALLE1IS for all trapped operations, > >> but you might want to see how that performs. > > > > That sounds reasonable for correctness. But I suspect we'll have to do > > more to claw back some performance. Let me run a few tests and come back > > on this. > > Assuming I've correctly switched in TCR and replacing the various TLB > operations in this patch with TLBI VMALLE1IS, there is a drop in kernel > build times of ~5% (384s vs 363s). What do you mean by "switched in TCR"? Why is that necessary if you just nuke the whole thing? Is the ~5% relative to no trapping at all, or trapping, but being selective about the operation? Will