Re: [RFC PATCH 1/1] Move two pinned pages to non-movable node in kvm.

Gleb Natapov
2014-06-30T06:00:47Z

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.