Re: [PATCH 0/4] kvm, mem-hotplug: Do not pin ept identity pagetable and apic access page.

From: Tang Chen
Date: Wed Jul 02 2014 - 21:17:19 EST


Hi Gleb,

On 07/02/2014 05:00 PM, Tang Chen wrote:
Hi Gleb, Marcelo,

Please help to review this patch-set.

NOTE: This patch-set doesn't work properly.


ept identity pagetable and apic access page in kvm are pinned in memory.
As a result, they cannot be migrated/hot-removed.

But actually they don't need to be pinned in memory.

This patch-set introduces two new vcpu requests: KVM_REQ_MIGRATE_EPT and KVM_REQ_MIGRATE_APIC.
These two requests are made when the two pages are migrated by the mmu_notifier
to reset the related variable to unusable value. And will also be made when
ept violation happens to reset new pages.


[Known problem]
After this patch-set applied, the two pages can be migrated/hot-removed.
But after migrating apic access page, the guest died.

The host physical address of apic access page is stored in VMCS. I reset
it to 0 to stop guest from accessing it when it is unmapped by
kvm_mmu_notifier_invalidate_page(). And reset it to new page's host physical
address in tdp_page_fault(). But it seems that guest will access apic page
directly by the host physical address.

Would you please to give some advice about this problem ?

Thanks.
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