From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947176AbcBRRSP (ORCPT ); Thu, 18 Feb 2016 12:18:15 -0500 Received: from mail-wm0-f49.google.com ([74.125.82.49]:33119 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1947119AbcBRRSK (ORCPT ); Thu, 18 Feb 2016 12:18:10 -0500 Subject: Re: [PART1 RFC 5/9] svm: Add VMEXIT handlers for AVIC To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <56C2C1BF.7010700@amd.com> <56C312E1.1080902@redhat.com> <20160216141330.GG10555@potion.brq.redhat.com> <56C354A5.4040807@redhat.com> <20160216180618.GA18952@potion.brq.redhat.com> <56C52B80.5050104@amd.com> <20160218141817.GA6289@potion.brq.redhat.com> <56C5DA62.8080204@redhat.com> <20160218154343.GA18904@potion.brq.redhat.com> <56C5E8E1.9060900@redhat.com> <20160218162701.GB6289@potion.brq.redhat.com> Cc: Suravee Suthikulpanit , joro@8bytes.org, alex.williamson@redhat.com, gleb@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, wei@redhat.com, sherry.hurwitz@amd.com, "Wu, Feng" From: Paolo Bonzini X-Enigmail-Draft-Status: N1110 Message-ID: <56C5FCCF.5010802@redhat.com> Date: Thu, 18 Feb 2016 18:18:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160218162701.GB6289@potion.brq.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 18/02/2016 17:27, Radim Krčmář wrote: > 2016-02-18 16:53+0100, Paolo Bonzini: >> Patch 9 is okay, but it is also necessary to clear IsRunning in >> kvm_arch_vcpu_blocking and set it in kvm_arch_vcpu_unblocking. In >> addition, vcpu_put/vcpu_load should not modify IsRunning between >> kvm_arch_vcpu_blocking and kvm_arch_vcpu_unblocking. Do you agree? > > Yes. > > I think we don't need to clear IsRunning on preemption, which would > simplify the protection. (I haven't thought much about userspace exit, > so maybe we could skip that one as well, but we don't need to now.) > > The reason for that is that KVM knows that the VCPU was scheduled out, > so it couldn't do much in the AVIC VMEXIT. > (KVM could force scheduler to pritioritize the VCPU, but our kick > doesn't do that now and it seems like a bad idea.) > > Does it seem reasonable? Yes, and in fact it wouldn't need to clear and set IsRunning on vcpu_put/vcpu_load; only on vcpu_blocking/vcpu_unblocking. The IsRunning flag is more of a IsNotHalted flag, in the end. Paolo