From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [GIT PULL] First batch of KVM changes for 4.1 Date: Wed, 22 Apr 2015 19:55:59 -0300 Message-ID: <20150422225559.GA21667@amt.cnet> References: <20150417105506.GF5029@twins.programming.kicks-ass.net> <553100C1.5000408@redhat.com> <20150417131037.GG23123@twins.programming.kicks-ass.net> <55310CF2.6070107@redhat.com> <20150417190146.GA24395@amt.cnet> <55316598.908@redhat.com> <20150417201841.GA31302@amt.cnet> <55353058.2000008@redhat.com> <20150422205602.GA15317@amt.cnet> <55380C3D.2080906@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, gleb@kernel.org, kvm@vger.kernel.org, Ralf Baechle , luto@kernel.org To: Paolo Bonzini Return-path: Content-Disposition: inline In-Reply-To: <55380C3D.2080906@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Wed, Apr 22, 2015 at 11:01:49PM +0200, Paolo Bonzini wrote: > > > On 22/04/2015 22:56, Marcelo Tosatti wrote: > >> > But then why was the task migration notifier even in Jeremy's original > >> > code for Xen? > > To cover for the vcpu1 -> vcpu2 -> vcpu1 case, i believe. > > Ok, to cover it for non-synchronized TSC. While KVM requires > synchronized TSC. > > > > If that's the case, then it could be reverted indeed; but then why did > > > you commit this patch to 4.1? > > > > Because it fixes the problem Andy reported (see Subject: KVM: x86: fix > > kvmclock write race (v2) on kvm@). As long as you have Radim's > > fix on top. > > But if it's so rare, and it was known that fixing the host protocol was > just as good a solution, why was the guest fix committed? I don't know. Should have fixed the host protocol. > I'm just trying to understand. I am worried that this patch was rushed > in; so far I had assumed it wasn't (a revert of a revert is rare enough > that you don't do it lightly...) but maybe I was wrong. Yes it was rushed in. > Right now I cannot even decide whether to revert it (and please Peter in > the process :)) or submit the Kconfig symbol patch officially. > > Paolo