Re: [PATCH 3/6] KVM: x86/mmu: avoid struct page in MMU

[Paolo Bonzini]

On 24/06/21 12:06, Marc Zyngier wrote:
> On Thu, 24 Jun 2021 09:58:00 +0100,
> Nicholas Piggin <npiggin@xxxxxxxxx> wrote:
> > Excerpts from David Stevens's message of June 24, 2021 1:57 pm:
> > > From: David Stevens <stevensd@xxxxxxxxxxxx>
> > >   out_unlock:
> > >   	if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))
> > >   		read_unlock(&vcpu->kvm->mmu_lock);
> > >   	else
> > >   		write_unlock(&vcpu->kvm->mmu_lock);
> > > -	kvm_release_pfn_clean(pfn);
> > > +	if (pfnpg.page)
> > > +		put_page(pfnpg.page);
> > >   	return r;
> > >   }
> >
> > How about
> >
> >    kvm_release_pfn_page_clean(pfnpg);
>
> I'm not sure. I always found kvm_release_pfn_clean() ugly, because it
> doesn't mark the page 'clean'. I find put_page() more correct.
>
> Something like 'kvm_put_pfn_page()' would make more sense, but I'm so
> bad at naming things that I could just as well call it 'bob()'.

The best way to go would be to get rid of kvm_release_pfn_clean() and 
always go through a pfn_page.  Then we could or could not introduce 
wrappers kvm_put_pfn_page{,_dirty}.

I think for now it's best to limit the churn since these patches will go 
in the stable releases too, and clean up the resulting API once we have 
a clear idea of how all architectures are using kvm_pfn_page.

Paolo