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    SubjectRe: [PATCH 3/4] kvm, memory-hotplug: Update ept identity pagetable when it is migrated.
    On Fri, Jul 04, 2014 at 10:36:06AM +0800, Tang Chen wrote:
    > Hi Gleb,
    >
    > On 07/03/2014 12:34 AM, Gleb Natapov wrote:
    > >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.
    >
    > We already have kvm->arch.ept_identity_pagetable_done to indicate if the ept
    > identity table is initialized. If we make kvm->arch.ept_identity_pagetable
    > to
    > bool, do you mean we have:
    >
    > kvm->arch.ept_identity_pagetable: indicate if ept page is allocated,
    > kvm->arch.ept_identity_pagetable_done: indicate if ept page is initialized ?
    >
    ept_identity_pagetable also means that a memory slot for identity page is initialized.

    > I don't think we need this. Shall we remove kvm->arch.ept_identity_pagetable
    > ?
    >
    May be those two can be consolidated somehow, but lets leave it to a separate patch
    to make this one simpler.

    --
    Gleb.


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