From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v3 05/10] KVM: arm/arm64: don't clear exit request from caller Date: Wed, 10 May 2017 14:19:12 +0200 Message-ID: <20170510121912.GD28721@cbox> References: <20170503160635.21669-1-drjones@redhat.com> <20170503160635.21669-6-drjones@redhat.com> <20170506181256.GB5923@cbox> <20170509171706.huhsia6lasf46bo6@kamzik.brq.redhat.com> <20170510095511.GB28721@cbox> <20170510100731.fag26qu3i3vgtg2c@kamzik.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, marc.zyngier@arm.com, pbonzini@redhat.com, rkrcmar@redhat.com To: Andrew Jones Return-path: Received: from mail-qk0-f169.google.com ([209.85.220.169]:34168 "EHLO mail-qk0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750733AbdEJMTT (ORCPT ); Wed, 10 May 2017 08:19:19 -0400 Received: by mail-qk0-f169.google.com with SMTP id k74so27274247qke.1 for ; Wed, 10 May 2017 05:19:18 -0700 (PDT) Content-Disposition: inline In-Reply-To: <20170510100731.fag26qu3i3vgtg2c@kamzik.brq.redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, May 10, 2017 at 12:07:31PM +0200, Andrew Jones wrote: > On Wed, May 10, 2017 at 11:55:11AM +0200, Christoffer Dall wrote: > > On Tue, May 09, 2017 at 07:17:06PM +0200, Andrew Jones wrote: > > > On Sat, May 06, 2017 at 08:12:56PM +0200, Christoffer Dall wrote: > > > > On Wed, May 03, 2017 at 06:06:30PM +0200, Andrew Jones wrote: > > > > > VCPU requests that the receiver should handle should only be cleared > > > > > by the receiver. > > > > > > > > I cannot parse this sentence. > > > > > > I'll try again: > > > > > > VCPU requests should only be cleared by the receiving VCPUs. The only > > > exception is when a request is set as a side-effect. In these cases > > > the "requester" threads may clear the requests when it is sure the > > > receiving VCPUs do not need to see them. > > > > > > > I can parse this, and I mostly understand this, except for the part > > about side-effects. > > E.g. kvm_vcpu_block(). This case isn't perfect, because the requester is > also the receiver, but the protocol applies to self-requests too, so it > still counts. Here KVM_REQ_UNHALT may be set as a side-effect of the call, > but on exit from the call, the caller may be sure that the receiver > (itself) doesn't care about the request, and thus can just clear it. > I see. You could mention this as an example if you like. Thanks, -Christoffer