Re: [PATCH 05/14] KVM: x86/mmu: Consult max mapping level when zapping collapsible SPTEs

Sean Christopherson
2021-02-18T18:28:41Z

On Thu, Feb 18, 2021, Paolo Bonzini wrote:
> On 13/02/21 01:50, Sean Christopherson wrote:
> >
> > pfn = spte_to_pfn(iter.old_spte);
> > if (kvm_is_reserved_pfn(pfn) ||
> > - (!PageTransCompoundMap(pfn_to_page(pfn)) &&
> > - !kvm_is_zone_device_pfn(pfn)))
> > + iter.level >= kvm_mmu_max_mapping_level(kvm, slot, iter.gfn,
> > + pfn, PG_LEVEL_NUM))
> > continue;
>
>
> This changes the test to PageCompound. Is it worth moving the change to
> patch 1?

Yes? I originally did that in a separate patch, then changed my mind.

If PageTransCompoundMap() also detects HugeTLB pages, then it is the "better"
option as it checks that the page is actually mapped huge. I dropped the change
because PageTransCompound() is just a wrapper around PageCompound(), and so I
assumed PageTransCompoundMap() would detect HugeTLB pages, too. I'm not so sure
about that after rereading the code, yet again.