Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758875AbaGOMxF (ORCPT ); Tue, 15 Jul 2014 08:53:05 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:63568 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1757665AbaGOMxD (ORCPT ); Tue, 15 Jul 2014 08:53:03 -0400 X-IronPort-AV: E=Sophos;i="5.00,896,1396972800"; d="scan'208";a="33293716" Message-ID: <53C52469.3060607@cn.fujitsu.com> Date: Tue, 15 Jul 2014 20:54:01 +0800 From: Tang Chen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Gleb Natapov CC: Jan Kiszka , , , , , , , Subject: Re: [PATCH v2 5/5] kvm, mem-hotplug: Do not pin apic access page in memory. 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> In-Reply-To: <20140715124048.GU18167@minantech.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.99] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. But sorry, a little strange. I didn't find where vmcs12->apic_access_addr is allocated or initialized... Would you please tell me ? > >> >> ...... >> 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 ? 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 ? Thanks. -- 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/