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 09:00:47 +0300
From:	Gleb Natapov <gleb@...nel.org>
To:	Tang Chen <tangchen@...fujitsu.com>
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>
Subject: Re: [RFC PATCH 1/1] Move two pinned pages to non-movable node in kvm.

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?

> 
> 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.

--
			Gleb.
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