Re: [PATCH 1/2] KVM: MMU: Do not treat ZONE_DEVICE pages as being reserved

[Paolo Bonzini]

On 11/11/19 19:27, Sean Christopherson wrote:
>> Thanks for this clarification. I do want to put out though that
>> ZONE_DEVICE pages go idle, they don't get freed. As long as KVM drops
>> its usage on invalidate it's perfectly fine for KVM to operate on idle
>> ZONE_DEVICE pages. The common case is that ZONE_DEVICE pages are
>> accessed and mapped while idle. Only direct-I/O temporarily marks them
>> busy to synchronize with invalidate. KVM obviates that need by
>> coordinating with mmu-notifiers instead.
> Only the KVM MMU, e.g. page fault handler, coordinates via mmu_notifier,
> the kvm_vcpu_map() case would continue using pages across an invalidate.

Yes, and it gets/puts the page correctly.

Paolo