From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [RFC PATCH 0/9] ACPI memory hotplug Date: Tue, 24 Apr 2012 10:21:31 +0300 Message-ID: <20120424072131.GI15413@redhat.com> References: <1334844527-18869-1-git-send-email-vasilis.liaskovitis@profitbricks.com> <20120422135618.GA15413@redhat.com> <4F941073.8090702@redhat.com> <20120422140945.GC15413@redhat.com> <4F941207.6050508@redhat.com> <20120422142059.GD15413@redhat.com> <4F955998.1070303@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Vasilis Liaskovitis , qemu-devel@nongnu.org, kvm@vger.kernel.org, seabios@seabios.org To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:52333 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754421Ab2DXHWM (ORCPT ); Tue, 24 Apr 2012 03:22:12 -0400 Content-Disposition: inline In-Reply-To: <4F955998.1070303@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Apr 23, 2012 at 04:31:04PM +0300, Avi Kivity wrote: > On 04/22/2012 05:20 PM, Gleb Natapov wrote: > > On Sun, Apr 22, 2012 at 05:13:27PM +0300, Avi Kivity wrote: > > > On 04/22/2012 05:09 PM, Gleb Natapov wrote: > > > > On Sun, Apr 22, 2012 at 05:06:43PM +0300, Avi Kivity wrote: > > > > > On 04/22/2012 04:56 PM, Gleb Natapov wrote: > > > > > > start. We will need it for migration anyway. > > > > > > > > > > > > > hotplug-able memory slots i.e. initial system memory is not modeled with > > > > > > > memslots. The concept could be generalized to include all memory though, or it > > > > > > > could more closely follow kvm-memory slots. > > > > > > OK, I hope final version will allow for memory < 4G to be hot-pluggable. > > > > > > > > > > Why is that important? > > > > > > > > > Because my feeling is that people that want to use this kind of feature > > > > what to start using it with VMs smaller than 4G. Of course not all > > > > memory have to be hot unpluggable. Making first 1M or event first 128M not > > > > unpluggable make perfect sense. > > > > > > Can't you achieve this with -m 1G, -device dimm,size=1G,populated=true > > > -device dimm,size=1G,populated=false? > > > > > From this: > > > > (for hw/pc.c PCI hole is currently [below_4g_mem_size, 4G), so > > hotplugged memory should start from max(4G, above_4g_mem_size). > > > > I understand that hotpluggable memory can start from above 4G only. With > > the config above we will have memory hole from 1G to PCI memory hole. > > May be not a big problem, but I do not see technical reason for the constrain. > > > > > (I don't think hotplugging below 512MB is needed, but I don't have any > > > real data on this). > > > > > 512MB looks like a reasonable limitation too, but again if there is not > > technical reason for having the limitation why have it? > > > > I was thinking about not having tons of 128MB slots, so we don't have a > configuration that is far from reality. But maybe this thinking is too > conservative. > I think it is good interface to make memory that is specified with -m to be one big unpluggable slot, but slots defined with -device should start just above what -m specifies (after proper alignment). Memory hot-plug granularity is controlled by slot's size parameter. -- Gleb.