linux-kernel - Re: [RFC PATCH 1/1] Move two pinned pages to non-movable node in kvm.

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Date:	Mon, 30 Jun 2014 16:58:10 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Gleb Natapov <gleb@...nel.org>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, <pbonzini@...hat.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<mgorman@...e.de>, <yinghai@...nel.org>,
	<isimatu.yasuaki@...fujitsu.com>, <guz.fnst@...fujitsu.com>,
	<laijs@...fujitsu.com>, <kvm@...r.kernel.org>,
	<linux-mm@...ck.org>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, Avi Kivity <avi.kivity@...il.com>,
	Tang Chen <tangchen@...fujitsu.com>
Subject: Re: [RFC PATCH 1/1] Move two pinned pages to non-movable node in
 kvm.

Hi Gleb,

On 06/30/2014 02:00 PM, Gleb Natapov wrote:
> On Mon, Jun 30, 2014 at 09:45:32AM +0800, Tang Chen wrote:
>> On 06/21/2014 04:39 AM, Marcelo Tosatti wrote:
>>> On Fri, Jun 20, 2014 at 05:31:46PM -0300, Marcelo Tosatti wrote:
>>>>> IIRC your shadow page pinning patch series support flushing of ptes
>>>>> by mmu notifier by forcing MMU reload and, as a result, faulting in of
>>>>> pinned pages during next entry.  Your patch series does not pin pages
>>>>> by elevating their page count.
>>>>
>>>> No but PEBS series does and its required to stop swap-out
>>>> of the page.
>>>
>>> Well actually no because of mmu notifiers.
>>>
>>> Tang, can you implement mmu notifiers for the other breaker of
>>> mem hotplug ?
>>
>> Hi Marcelo,
>>
>> I made a patch to update ept and apic pages when finding them in the
>> next ept violation. And I also updated the APIC_ACCESS_ADDR phys_addr.
>> The pages can be migrated, but the guest crached.
> How does it crash?

It just stopped running. The guest system is dead.
I'll try to debug it and give some more info.

>
>>
>> How do I stop guest from access apic pages in mmu_notifier when the
>> page migration starts ?  Do I need to stop all the vcpus by set vcpu
>> state to KVM_MP_STATE_HALTED ?  If so, the vcpu will not able to go
>> to the next ept violation.
> When apic access page is unmapped from ept pages by mmu notifiers you
> need to set its value in VMCS to a physical address that will never be
> mapped into guest memory. Zero for instance. You can do it by introducing
> new KVM_REQ_ bit and set VMCS value during next vcpu's vmentry. On ept
> violation you need to update VMCS pointer to newly allocated physical
> address, you can use the same KVM_REQ_ mechanism again.
>
>>
>> So, may I write any specific value into APIC_ACCESS_ADDR to stop guest
>> from access to apic page ?
>>
> Any phys address that will never be mapped into guest's memory should work.

Thanks for the advice. I'll try it.

Thanks.
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