From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: Cleaning up the KVM clock Date: Mon, 22 Dec 2014 23:47:40 +0100 Message-ID: <54989F8C.3030602@redhat.com> References: <20141222133430.GA23631@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 22/12/2014 17:03, Andy Lutomirski wrote: > > This is wrong. The guest *kernel* might not see the intermediate > state because the kernel (presumably it disabled migration while > reading pvti), but the guest vdso can't do that and could very easily > observe pvti while it's being written. No. kvm_guest_time_update is called by vcpu_enter_guest, while the vCPU is not running, so it's entirely atomic from the point of view of the guest. > I'll send patches for the whole mess, complete with lots of comments, > after I test them a bit today. Ok, some comments can certainly help the discussion. Paolo