linux-kernel - Re: [PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable when it is migrated.

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Message-ID: <20140702163420.GC4399@minantech.com>
Date:	Wed, 2 Jul 2014 19:34:20 +0300
From:	Gleb Natapov <gleb@...nel.org>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	mtosatti@...hat.com, kvm@...r.kernel.org, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, guz.fnst@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable
 when it is migrated.

On Wed, Jul 02, 2014 at 05:00:36PM +0800, Tang Chen wrote:
> ept identity pagetable is pinned in memory, and as a result it cannot be
> migrated/hot-removed.
> 
> But actually it doesn't need to be pinned in memory.
> 
> This patch introduces a new vcpu request: KVM_REQ_MIGRATE_EPT to reset ept
> indetity pagetable related variable. This request will be made when
> kvm_mmu_notifier_invalidate_page() is called when the page is unmapped
> from the qemu user space to reset kvm->arch.ept_identity_pagetable to NULL.
> And will also be made when ept violation happens to reset
> kvm->arch.ept_identity_pagetable to the new page.

kvm->arch.ept_identity_pagetable is never used as a page address, just
boolean null/!null to see if identity pagetable is initialized. I do
not see why would we want to track its address at all. Changing it to bool
and assigning true during initialization should be enough.


--
			Gleb.
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