From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PART1 RFC 5/9] svm: Add VMEXIT handlers for AVIC Date: Thu, 18 Feb 2016 18:18:07 +0100 Message-ID: <56C5FCCF.5010802@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE 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" To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Return-path: In-Reply-To: <20160218162701.GB6289@potion.brq.redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 18/02/2016 17:27, Radim Kr=C4=8Dm=C3=A1=C5=99 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? >=20 > Yes. >=20 > I think we don't need to clear IsRunning on preemption, which would > simplify the protection. (I haven't thought much about userspace exi= t, > so maybe we could skip that one as well, but we don't need to now.) >=20 > 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.) >=20 > 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