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

[Tang Chen]

Hi Gleb,

On 06/30/2014 02:00 PM, Gleb Natapov wrote:
> 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?

It just stopped running. The guest system is dead.
I'll try to debug it and give some more info.

> > 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.

Thanks for the advice. I'll try it.

Thanks.
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