On Wed, May 14, 2025 at 06:59:01AM +0800, Edgecombe, Rick P wrote:
> On Thu, 2025-04-24 at 11:08 +0800, Yan Zhao wrote:
> > +static int kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t start,
> > + pgoff_t end, bool need_split)
> > {
> > bool flush = false, found_memslot = false;
> > struct kvm_memory_slot *slot;
> > struct kvm *kvm = gmem->kvm;
> > unsigned long index;
> > + int ret = 0;
> >
> > xa_for_each_range(&gmem->bindings, index, slot, start, end - 1) {
> > pgoff_t pgoff = slot->gmem.pgoff;
> > @@ -319,14 +320,23 @@ static void kvm_gmem_invalidate_begin(struct kvm_gmem *gmem, pgoff_t start,
> > kvm_mmu_invalidate_begin(kvm);
> > }
> >
> > + if (need_split) {
> > + ret = kvm_split_boundary_leafs(kvm, &gfn_range);
>
> What is the effect for other guestmemfd users? SEV doesn't need this, right? Oh
> I see, down in tdp_mmu_split_boundary_leafs() it bails on non-mirror roots. I
> don't like the naming then. It sounds deterministic, but it's really only
> necessary splits for certain VM types.
Right, kvm_split_boundary_leafs() only takes effect on the mirror root.
> I guess it all depends on how well teaching kvm_mmu_unmap_gfn_range() to fail
> goes. But otherwise, we should call it like kvm_prepare_zap_range() or
Hmm, if we call it kvm_prepare_zap_range(), we have to invoke it for all zaps.
However, except kvm_gmem_punch_hole(), the other two callers
kvm_gmem_error_folio(), kvm_gmem_release() have no need to perfrom splitting
before zapping.
Passing in the invalidation reason to kvm_gmem_invalidate_begin() also makes
things complicated.
> something. And have it make it clearly do nothing for non-TDX high up where it's
> easy to see.
Would a name like kvm_split_boundary_leafs_for_mirror() be too TDX specific?
If we name it kvm_split_boundary_leafs(), SEV can simply remove the bailing out
if they want in future.
>
> > + if (ret < 0)
> > + goto out;
> > +
> > + flush |= ret;
> > + }
> > flush |= kvm_mmu_unmap_gfn_range(kvm, &gfn_range);
> > }
> >
> > +out:
> > if (flush)
> > kvm_flush_remote_tlbs(kvm);
> >
> > if (found_memslot)
> > KVM_MMU_UNLOCK(kvm);
> > +
>
