From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nadav Amit Subject: Re: [PATCH 4/4] kvm, mem-hotplug: Update apic access page when it is migrated. Date: Mon, 07 Jul 2014 15:10:23 +0300 Message-ID: <53BA8E2F.9000200@gmail.com> References: <1404291637-15048-1-git-send-email-tangchen@cn.fujitsu.com> <1404291637-15048-5-git-send-email-tangchen@cn.fujitsu.com> <20140703135507.GM18167@minantech.com> <53B60EF1.6030307@cn.fujitsu.com> <20140704101310.GE4399@minantech.com> <53BA6DD3.9040400@cn.fujitsu.com> <53BA87A3.5020205@gmail.com> <20140707115446.GP18167@minantech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Tang Chen , mtosatti@redhat.com, kvm@vger.kernel.org, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, guz.fnst@cn.fujitsu.com, linux-kernel@vger.kernel.org To: Gleb Natapov Return-path: In-Reply-To: <20140707115446.GP18167@minantech.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 7/7/14, 2:54 PM, Gleb Natapov wrote: > On Mon, Jul 07, 2014 at 02:42:27PM +0300, Nadav Amit wrote: >> Tang, >> >> Running some (unrelated) tests I see that KVM does not handle APIC base >> relocation correctly. When the base is changed, kvm_lapic_set_base just >> changes lapic->base_address without taking further action (i.e., modifying >> the VMCS apic address in VMX). >> >> This patch follows KVM bad behavior by using the constant >> VMX_APIC_ACCESS_PAGE_ADDR instead of lapic->base_address. > There is no OS out there that relocates APIC base (in fact it was not always > relocatable on real HW), so there is not point in complicating the code to support > it. In fact current APIC_ACCESS_ADDR handling relies on the fact that all vcpus > has apic mapped at the same address. > >> >> Anyhow, I didn't see anything that would make my life (in fixing the lapic >> base issue) too difficult. Yet, feel free in making it more "fix-friendly". >> > Why would you want to fix it? > If there is no general need, I will not send a fix. However, I think the very least a warning message should be appear if the guest relocates the APIC base. Nadav