From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933707AbaJaPG7 (ORCPT ); Fri, 31 Oct 2014 11:06:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39034 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932570AbaJaPG5 (ORCPT ); Fri, 31 Oct 2014 11:06:57 -0400 Message-ID: <5453A589.6040308@redhat.com> Date: Fri, 31 Oct 2014 16:06:49 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , linux-kernel@vger.kernel.org CC: kvm@vger.kernel.org, Gleb Natapov , Marcelo Tosatti Subject: Re: [PATCH 0/3] kvm: APICv register write workaround References: <1414678007-9377-1-git-send-email-rkrcmar@redhat.com> In-Reply-To: <1414678007-9377-1-git-send-email-rkrcmar@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 30/10/2014 15:06, Radim Krčmář wrote: > APICv traps register writes, so we can't retrieve previous value, but > our code depends on detecting changes. Applied, thanks. Paolo > Apart from disabling APIC register virtualization, we can detect the > change by using extra memory. One value history is enough, but we still > don't want to keep it for every APIC register, for performance reasons. > This leaves us with either a new framework, or exceptions ... > The latter options fits KVM's path better [1,2]. > > And when we already mirror a part of registers, optimizing access is > acceptable [3]. (Squashed to keep bisecters happy.) > > --- > Radim Krčmář (3): > KVM: x86: detect SPIV changes under APICv > KVM: x86: detect LVTT changes under APICv > KVM: x86: optimize some accesses to LVTT and SPIV > > arch/x86/kvm/lapic.c | 32 +++++++++++++++++--------------- > arch/x86/kvm/lapic.h | 8 +++++--- > 2 files changed, 22 insertions(+), 18 deletions(-) >