From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754152AbaIKLa7 (ORCPT ); Thu, 11 Sep 2014 07:30:59 -0400 Received: from mail-we0-f181.google.com ([74.125.82.181]:46846 "EHLO mail-we0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751166AbaIKLa5 (ORCPT ); Thu, 11 Sep 2014 07:30:57 -0400 Date: Thu, 11 Sep 2014 14:30:51 +0300 From: Gleb Natapov To: Paolo Bonzini Cc: Tang Chen , mtosatti@redhat.com, nadav.amit@gmail.com, jan.kiszka@web.de, kvm@vger.kernel.org, laijs@cn.fujitsu.com, isimatu.yasuaki@jp.fujitsu.com, guz.fnst@cn.fujitsu.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5 4/7] kvm, mem-hotplug: Reload L1' apic access page on migration in vcpu_enter_guest(). Message-ID: <20140911113051.GG25317@minantech.com> References: <1410413886-32213-1-git-send-email-tangchen@cn.fujitsu.com> <1410413886-32213-5-git-send-email-tangchen@cn.fujitsu.com> <541169AD.6060908@redhat.com> <20140911101200.GF25317@minantech.com> <54117DB4.307@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54117DB4.307@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 11, 2014 at 12:47:16PM +0200, Paolo Bonzini wrote: > Il 11/09/2014 12:12, Gleb Natapov ha scritto: > > On Thu, Sep 11, 2014 at 11:21:49AM +0200, Paolo Bonzini wrote: > >> Il 11/09/2014 07:38, Tang Chen ha scritto: > >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > >>> index 63c4c3e..da6d55d 100644 > >>> --- a/arch/x86/kvm/vmx.c > >>> +++ b/arch/x86/kvm/vmx.c > >>> @@ -7093,6 +7093,11 @@ static void vmx_set_virtual_x2apic_mode(struct kvm_vcpu *vcpu, bool set) > >>> vmx_set_msr_bitmap(vcpu); > >>> } > >>> > >>> +static void vmx_set_apic_access_page_addr(struct kvm *kvm, hpa_t hpa) > >>> +{ > >>> + vmcs_write64(APIC_ACCESS_ADDR, hpa); > >> > >> This has to be guarded by "if (!is_guest_mode(vcpu))". > >> > > We do need to write it if L1 and L2 share APIC_ACCESS_ADDR and skip > > it otherwise, no? > > Yes, but this would be handled by patch 6: > > } else if (vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) { > + struct page *page = gfn_to_page(vmx->vcpu.kvm, > + APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT); > exec_control |= > SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES; > - vmcs_write64(APIC_ACCESS_ADDR, > - page_to_phys(vcpu->kvm->arch.apic_access_page)); > + vmcs_write64(APIC_ACCESS_ADDR, page_to_phys(page)); > + /* > + * Do not pin apic access page in memory so that memory > + * hotplug process is able to migrate it. > + */ > + put_page(page); > } This code is in prepare_vmcs02() and is executed during L1->L2 vmentry. What happens when apic access page is migrated while L2 is running? It needs to be update somewhere. > > However, this is also useless code duplication because the above snippet could > reuse vcpu_reload_apic_access_page too. > > So I think you cannot do the is_guest_mode check in > kvm_vcpu_reload_apic_access_page and also not in > vmx_reload_apic_access_page. But you could do something like > > kvm_vcpu_reload_apic_access_page(...) > { > ... > kvm_x86_ops->reload_apic_access_page(...); > } > EXPORT_SYMBOL_GPL(kvm_vcpu_reload_apic_access_page); > > /* used in vcpu_enter_guest only */ > vcpu_reload_apic_access_page(...) > { > if (!is_guest_mode(vcpu)) > kvm_vcpu_reload_apic_access_page(...) > } > > Paolo -- Gleb.