From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch] kvm: make cr3 loading more robust Date: Thu, 04 Jan 2007 10:58:36 +0200 Message-ID: <459CC1BC.3070308@qumranet.com> References: <20070103021057.GA11316@elte.hu> <459B695C.5090004@qumranet.com> <20070103115911.GA2786@elte.hu> <459B9C5C.9060008@qumranet.com> <20070103122114.GD2786@elte.hu> <459BA194.8070305@qumranet.com> <20070103123253.GA8822@elte.hu> <20070103133714.GA20638@elte.hu> <20070103134417.GA22055@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel Return-path: To: Ingo Molnar In-Reply-To: <20070103134417.GA22055-X9Un+BFzKDI@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Ingo Molnar wrote: > another small detail is that currently KVM_SET_MEMORY_REGION appears to > be an add-only interface - it is not possible to 'unregister' RAM from a > VM. > Well, the _interface_ supports removing, the implementation does not :) Everything was written in mind to allow memory hotplug. > That keeps things easy for now, but if it's ever implemented then the > current cr3 of all vcpus of the VM needs to be validated against the > reduced memory slot map. (besides migrating all existing mappings from > the removed memory slot to other memory slots and redirecting all > in-flight DMA transactions, etc., etc. Which all needs heavy guest-OS > awareness as well.) > Actually I think it's quite easy: - halt all vcpus - wait for dma to complete - mmu_free_roots() - zap all page tables - actually unplug memory - mmu_alloc_roots() The guest needs to cooperate, but it can do so using the native memory hotlpug mechanisms (whatever they are). No guest modifications are needed. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV