Re: [RFC PATCH 18/32] KVM: PPC: Book3S HV: Use kvmppc_unmap_pte() in kvm_unmap_radix()

[Paul Mackerras <paulus@ozlabs.org>]

On Wed, Sep 26, 2018 at 02:30:02PM +1000, David Gibson wrote:
> On Wed, Sep 26, 2018 at 02:08:37PM +1000, David Gibson wrote:
> > >  static void kvmppc_unmap_pte(struct kvm *kvm, pte_t *pte,
> > > -			     unsigned long gpa, unsigned int shift)
> > > +			     unsigned long gpa, unsigned int shift,
> > > +			     struct kvm_memory_slot *memslot)
> > >  
> > >  {
> > > -	unsigned long page_size = 1ul << shift;
> > >  	unsigned long old;
> > >  
> > >  	old = kvmppc_radix_update_pte(kvm, pte, ~0UL, 0, gpa, shift);
> > >  	kvmppc_radix_tlbie_page(kvm, gpa, shift);
> > >  	if (old & _PAGE_DIRTY) {
> > >  		unsigned long gfn = gpa >> PAGE_SHIFT;
> > > -		struct kvm_memory_slot *memslot;
> > > +		unsigned long page_size = PAGE_SIZE;
> > >  
> > > -		memslot = gfn_to_memslot(kvm, gfn);
> > > -		if (memslot && memslot->dirty_bitmap)
> > > +		if (shift)
> > > +			page_size = 1ul << shift;
> > > +		if (!memslot)
> > > +			memslot = gfn_to_memslot(kvm, gfn);
> 
> ..it might be nicer to avoid the explicit test on memslot by maping a
> __kvmppc_unmap_pte() which must have memslot passed in, and a wrapper
> which computes it from the gfn.

Then we would be looking up the memslot even when we aren't going to
use it.  In a subsequent patch this function gets used on shadow page
tables and in that case we never need the memslot.

Paul.