Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754202AbaGOOkm (ORCPT ); Tue, 15 Jul 2014 10:40:42 -0400 Received: from mail-we0-f171.google.com ([74.125.82.171]:37748 "EHLO mail-we0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753717AbaGOOkg (ORCPT ); Tue, 15 Jul 2014 10:40:36 -0400 Date: Tue, 15 Jul 2014 17:40:31 +0300 From: Gleb Natapov To: Tang Chen Cc: Jan Kiszka , mtosatti@redhat.com, nadav.amit@gmail.com, 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 v2 5/5] kvm, mem-hotplug: Do not pin apic access page in memory. Message-ID: <20140715144030.GN4399@minantech.com> References: <1404824492-30095-1-git-send-email-tangchen@cn.fujitsu.com> <1404824492-30095-6-git-send-email-tangchen@cn.fujitsu.com> <20140712080442.GH4399@minantech.com> <53C38D55.2040307@cn.fujitsu.com> <20140714145822.GK4399@minantech.com> <53C51608.4080109@web.de> <20140715120921.GT18167@minantech.com> <53C51E66.7030208@cn.fujitsu.com> <20140715124048.GU18167@minantech.com> <53C52469.3060607@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53C52469.3060607@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 15, 2014 at 08:54:01PM +0800, Tang Chen wrote: > On 07/15/2014 08:40 PM, Gleb Natapov wrote: > >On Tue, Jul 15, 2014 at 08:28:22PM +0800, Tang Chen wrote: > >>On 07/15/2014 08:09 PM, Gleb Natapov wrote: > >>>On Tue, Jul 15, 2014 at 01:52:40PM +0200, Jan Kiszka wrote: > >>...... > >>>> > >>>>I cannot follow your concerns yet. Specifically, how should > >>>>APIC_ACCESS_ADDR (the VMCS field, right?) change while L2 is running? We > >>>>currently pin/unpin on L1->L2/L2->L1, respectively. Or what do you mean? > >>>> > >>>I am talking about this case: > >>> if (cpu_has_secondary_exec_ctrls()) {a > >>> } else { > >>> exec_control |= > >>> SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES; > >>> vmcs_write64(APIC_ACCESS_ADDR, > >>> page_to_phys(vcpu->kvm->arch.apic_access_page)); > >>> } > >>>We do not pin here. > >>> > >> > >>Hi Gleb, > >> > >> > >>7905 if (exec_control& > >>SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES) { > >>...... > >>7912 if (vmx->nested.apic_access_page) /* shouldn't > >>happen */ > >>7913 nested_release_page(vmx->nested.apic_access_page); > >>7914 vmx->nested.apic_access_page = > >>7915 nested_get_page(vcpu, > >>vmcs12->apic_access_addr); > >> > >>I thought you were talking about the problem here. We pin > >>vmcs12->apic_access_addr > >>in memory. And I think we should do the same thing to this page as to L1 vm. > >>Right ? > >Nested kvm pins a lot of pages, it will probably be not easy to handle all of them, > >so for now I am concerned with non nested case only (but nested should continue to > >work obviously, just pin pages like it does now). > > True. I will work on it. > > And also, when using PCI passthrough, kvm_pin_pages() also pins some pages. > This is > also in my todo list. Those pages are (almost) directly accessible by assigned PCI devices, I am not sure this is even doable. > > But sorry, a little strange. I didn't find where vmcs12->apic_access_addr is > allocated > or initialized... Would you please tell me ? handle_vmwrite() writes it when guest is executing vmwrite(APIC_ACCESS_ADDR); > > > > >> > >>...... > >>7922 if (!vmx->nested.apic_access_page) > >>7923 exec_control&= > >>7924 ~SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES; > >>7925 else > >>7926 vmcs_write64(APIC_ACCESS_ADDR, > >>7927 page_to_phys(vmx->nested.apic_access_page)); > >>7928 } else if > >>(vm_need_virtualize_apic_accesses(vmx->vcpu.kvm)) { > >>7929 exec_control |= > >>7930 SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES; > >>7931 vmcs_write64(APIC_ACCESS_ADDR, > >>7932 page_to_phys(vcpu->kvm->arch.apic_access_page)); > >>7933 } > >> > >>And yes, we have the problem you said here. We can migrate the page while L2 > >>vm is running. > >>So I think we should enforce L2 vm to exit to L1. Right ? > >> > >We can request APIC_ACCESS_ADDR reload during L2->L1 vmexit emulation, so > >if APIC_ACCESS_ADDR changes while L2 is running it will be reloaded for L1 too. > > > > apic pages for L2 and L1 are not the same page, right ? > If L2 guest enable apic access page then they are different, otherwise they are the same. > I think, just like we are doing in patch 5/5, we cannot wait for the next > L2->L1 vmexit. > We should enforce a L2->L1 vmexit in mmu_notifier, just like > make_all_cpus_request() does. > > Am I right ? > I do not see why forcing APIC_ACCESS_ADDR reload during L2->L1 exit is not enough. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/