From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tang Chen <tangchen@cn.fujitsu.com>
Subject: Re: [PATCH v2 5/5] kvm, mem-hotplug: Do not pin apic access page
 in memory.
Date: Tue, 15 Jul 2014 20:28:22 +0800
Message-ID: <53C51E66.7030208@cn.fujitsu.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>
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Cc: Jan Kiszka <jan.kiszka@web.de>, <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>
To: Gleb Natapov <gleb@kernel.org>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20140715120921.GT18167@minantech.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

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 ?

......
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 ?

Thanks.