From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [KVM TSC trapping / migration 2/2] Add TSC KHZ MSR Date: Thu, 06 Jan 2011 01:27:12 -1000 Message-ID: <4D25A710.5030500@redhat.com> References: <1294308645-31113-1-git-send-email-zamsden@redhat.com> <1294308645-31113-3-git-send-email-zamsden@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Alexander Graf Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 01/06/2011 12:34 AM, Alexander Graf wrote: > Am 06.01.2011 um 11:10 schrieb Zachary Amsden: > > >> Use an MSR to allow "soft" migration to hosts which do not support >> TSC trapping. Rather than make this a required element of any >> migration protocol, we allow the TSC rate to be exported as a data >> field (useful in its own right), but we also allow a one time write >> of the MSR during VM creation. The result is that for the common >> use case, no protocol change is required to communicate TSC rate >> to the receiving host. >> >> This allows administrative tools to configure migration policy >> as they see appropriate. Rather than dictate this policy with the >> KVM implementation, we properly allow migration to hosts which both >> do and do not support setting of the TSC rate on the receiving end. >> If it is wished to not support migration to a host which lacks >> support for the TSC rate feature, that can be coordinated externally. >> > Isn't there a real hw equivalent of such a register? It might make more sense to just implement that then. > > Unfortunately, no.