Re: [PATCH v2 20/26] KVM: x86/mmu: Extend Eager Page Splitting to the shadow MMU

Peter Xu
2022-03-30T18:36:38Z

On Tue, Mar 22, 2022 at 04:58:08PM -0700, David Matlack wrote:
> > > +static int prepare_to_split_huge_page(struct kvm *kvm,
> > > + const struct kvm_memory_slot *slot,
> > > + u64 *huge_sptep,
> > > + struct kvm_mmu_page **spp,
> > > + bool *flush,
> > > + bool *dropped_lock)
> > > +{
> > > + int r = 0;
> > > +
> > > + *dropped_lock = false;
> > > +
> > > + if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES)
> > > + return -ENOSPC;
> > > +
> > > + if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
> > > + goto drop_lock;
> > > +
> >
> > Not immediately clear on whether there'll be case that *spp is set within
> > the current function. Some sanity check might be nice?
>
> Sorry I'm not sure what you mean here. What kind of sanity check did
> you have in mind?

Something like "WARN_ON_ONCE(*spp);"?

>
> >
> > > + *spp = kvm_mmu_alloc_direct_sp_for_split(true);
> > > + if (r)
> > > + goto drop_lock;
> > > +
> > > + return 0;

Thanks,

--
Peter Xu