Messages in this thread | | | Date | Fri, 4 Jul 2014 14:41:57 +0800 | From | Tang Chen <> | Subject | Re: [PATCH 0/4] kvm, mem-hotplug: Do not pin ept identity pagetable and apic access page. |
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Hi Gleb,
On 07/03/2014 02:04 PM, Gleb Natapov wrote: > On Thu, Jul 03, 2014 at 09:17:59AM +0800, Tang Chen wrote: >> 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 ? >> > I haven't reviewed third patch yet, will do ASAP. >
I printed some info in the kernel, and I found that mmu_notifier unmapped the apic page and set VMCS APIC_ACCESS_ADDR to 0. But apic page ept violation didn't happen. And the guest stopped running.
I think when guest tried to access apic page, there was no ept violation happened. And as a result, VMCS APIC_ACCESS_ADDR was not correctly set.
Referring to Intel Software Developer's Manuel Vol 3B, when accessing apic page using translation with a large page (2M, 4M, 1G), APIC VM_exit will not happen.
How do you think about this ?
Thanks. :)
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