Re: [PATCH v12 54/84] KVM: arm64: Mark "struct page" pfns accessed/dirty before dropping mmu_lock

Sean Christopherson
2024-08-05T23:53:40Z

On Mon, Aug 05, 2024, Oliver Upton wrote:
> > > ---
> > > arch/arm64/kvm/mmu.c | 10 ++++++----
> > > 1 file changed, 6 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> > > index 22ee37360c4e..ce13c3d884d5 100644
> > > --- a/arch/arm64/kvm/mmu.c
> > > +++ b/arch/arm64/kvm/mmu.c
> > > @@ -1685,15 +1685,17 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> > > }
> > >
> > > out_unlock:
> > > + if (writable && !ret)
> > > + kvm_set_pfn_dirty(pfn);
> >
> > I'm guessing you meant kvm_release_pfn_dirty() here, because this leaks
> > a reference.

Doh, I did indeed. Alternatively, this could be:

if (writable && !ret)
kvm_set_pfn_dirty(pfn);

kvm_release_pfn_clean(pfn);

It won't matter in the end, because this just becomes:

kvm_release_faultin_page(kvm, page, !!ret, writable);

So I guess the question is if you prefer to make the switch to an if-else in this
path, or more implicitly in the conversion to kvm_release_faultin_page().

I made the same goof for RISC-V, perhaps to prove that I too can copy+paste arm64's
MMU code ;-)