[PATCH 5/6 v2] kvm: powerpc: booke: Add linux pte lookup like booke3s

[Scott Wood]

On Wed, 2013-08-07 at 10:24 +1000, Paul Mackerras wrote:
> On Tue, Aug 06, 2013 at 07:02:48AM +0000, Bhushan Bharat-R65777 wrote:
> > 
> > I am trying to me the Linux pte search and update generic so that this can be used for powerpc as well.
> > 
> > I am not sure which of the below two should be ok, please help
> 
> Given that the BookE code uses gfn_to_pfn_memslot() to get the host
> pfn, and then kvm_set_pfn_dirty(pfn) on pages that you're going to let
> the guest write to, I don't think you need to set the dirty and/or
> accessed bits in the Linux PTE explicitly.  If you care about the
> WIMGE bits you can do find_linux_pte_or_hugepte() and just look at the
> PTE, but you really should be using mmu_notifier_retry() to guard
> against concurrent changes to the Linux PTE.  See the HV KVM code or
> patch 21 of my recent series to see how it's used. 

Hmm... we only get a callback on invalidate_range_start(), not
invalidate_range_end() (and even if we did get a callback for the
latter, it'd probably be racy).  So we may have a problem here
regardless of getting WIMG from the PTE, unless it's guaranteed that
hva_to_pfn() will fail after invalidate_range_start().

>  You probably should be calling kvm_set_pfn_accessed() as well.

Yeah...  I think it'll only affect the quality of page-out decisions (as
opposed to corruption and such), but still it should be fixed.

-Scott