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

[Sean Christopherson]

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.