+Ritesh as well
On Mon, Nov 02, 2026, Sean Christopherson wrote:
> +Gautam and PPC lists/maintainers
>
> On Fri, Oct 30, 2026, [email protected] wrote:
> > Thank you for your contribution! Sashiko AI review found 1 potential
> > issue(s) to consider:
> > - [Medium] KVM: PPC: Book3S HV: rmap_nested memory leak in
> > kvmhv_release_all_nested()
> > --
> >
> > commit 9c25a1b4a76e8526eb8a2b11e1b9e63893b0de80
> > Author: Sean Christopherson <[email protected]>
> >
> > KVM: Destroy memslots immediately after mmu_notifiers are unregistered
> >
> > This commit replaces active memslots with an empty memslot set and frees all
> > memslots immediately after unregistering the MMU notifier in
> > kvm_destroy_vm(),
> > prior to calling kvm_arch_destroy_vm().
> >
> > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > > index fa548b12228ff..2eda12a52bf4b 100644
> > > --- a/virt/kvm/kvm_main.c
> > > +++ b/virt/kvm/kvm_main.c
> >
> > [ ... ]
> >
> > > @@ -1310,12 +1329,10 @@ static void kvm_destroy_vm(struct kvm *kvm)
> > > kvm->mn_active_invalidate_count = 0;
> > > else
> > > WARN_ON(kvm->mmu_invalidate_in_progress);
> > > + kvm_destroy_memslots(kvm);
> > > +
> > > kvm_arch_destroy_vm(kvm);
> > > kvm_destroy_devices(kvm);
> > > - for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
> > > - kvm_free_memslots(kvm, &kvm->__memslots[i][0]);
> > > - kvm_free_memslots(kvm, &kvm->__memslots[i][1]);
> > > - }
> >
> > [Severity: Medium]
> > Does hoisting kvm_destroy_memslots() above kvm_arch_destroy_vm() leak
> > struct rmap_nested allocations in slot->arch.rmap on PowerPC Book3S HV when
> > destroying a VM with nested virtualization enabled?
>
> I don't think so? Patch 3[*], "KVM: PPC: Flush/zap all memslots on
> kvm_arch_flush_shadow_all()",
> should free the rmaps in response to kvm_arch_flush_shadow_all(). From what
> I
> can tell, the page tables have to be in radix mode, and so the rmaps are
> freed via:
>
> kvmppc_radix_flush_memslot()
> |
> -> kvmppc_unmap_pte()
> |
> -> kvmhv_remove_nest_rmap_range()
> |
> -> kvmhv_remove_nest_rmap_list()
>
> And if that doesn't work, it means memslot deletion on an active VM is
> completely
> broken.
>
> However, it means the memslot code in kvmhv_release_all_nested() is dead
> code, so
> this as follow-up to patch 3? Or maybe folded in?
>
> diff --git a/arch/powerpc/kvm/book3s_hv_nested.c
> b/arch/powerpc/kvm/book3s_hv_nested.c
> index a6ff42d7666c..27985210f972 100644
> --- a/arch/powerpc/kvm/book3s_hv_nested.c
> +++ b/arch/powerpc/kvm/book3s_hv_nested.c
> @@ -802,8 +802,6 @@ void kvmhv_release_all_nested(struct kvm *kvm)
> int lpid;
> struct kvm_nested_guest *gp;
> struct kvm_nested_guest *freelist = NULL;
> - struct kvm_memory_slot *memslot;
> - int srcu_idx, bkt;
>
> spin_lock(&kvm->mmu_lock);
> idr_for_each_entry(&kvm->arch.kvm_nested_guest_idr, gp, lpid) {
> @@ -820,11 +818,6 @@ void kvmhv_release_all_nested(struct kvm *kvm)
> freelist = gp->next;
> kvmhv_release_nested(gp);
> }
> -
> - srcu_idx = srcu_read_lock(&kvm->srcu);
> - kvm_for_each_memslot(memslot, bkt, kvm_memslots(kvm))
> - kvmhv_free_memslot_nest_rmap(memslot);
> - srcu_read_unlock(&kvm->srcu, srcu_idx);
> }
>
> /* caller must hold gp->tlb_lock */
>
>
> [*] https://lore.kernel.org/all/[email protected]
>
> > In virt/kvm/kvm_main.c, kvm_destroy_memslots() replaces kvm->memslots[i]
> > with kvm_empty_memslots and frees each memslot via
> > kvm_free_memslot() -> kvm_arch_free_memslot() ->
> > kvmppc_core_free_memslot_hv()
> > in arch/powerpc/kvm/book3s_hv.c:
> >
> > static void kvmppc_core_free_memslot_hv(struct kvm_memory_slot *slot)
> > {
> > vfree(slot->arch.rmap);
> > slot->arch.rmap = NULL;
> > }
> >
> > which frees the slot->arch.rmap array without freeing the linked
> > struct rmap_nested entries.
> >
> > Previously, those entries were freed before memslot destruction via
> > kvm_arch_destroy_vm() -> kvmppc_core_destroy_vm_hv() ->
> > kvmhv_release_all_nested() in arch/powerpc/kvm/book3s_hv_nested.c:
> >
> > srcu_idx = srcu_read_lock(&kvm->srcu);
> > kvm_for_each_memslot(memslot, bkt, kvm_memslots(kvm))
> > kvmhv_free_memslot_nest_rmap(memslot);
> > srcu_read_unlock(&kvm->srcu, srcu_idx);
> >
> > With kvm_destroy_memslots() running before kvm_arch_destroy_vm(),
> > kvm_memslots(kvm) now returns kvm_empty_memslots and the memslots have
> > already been freed when kvmhv_release_all_nested() runs, so
> > kvmhv_free_memslot_nest_rmap() is never called. Any struct rmap_nested
> > entries remaining in slot->arch.rmap at teardown (for example, when
> > KVMPPC_SECURE_INIT_DONE causes kvmppc_radix_flush_memslot() to return early,
> > or when 4KB PTEs were replaced by a huge page in kvmppc_unmap_free_pte())
> > will be leaked.
> >
> > --
> > Sashiko AI review ยท
> > https://sashiko.dev/#/patchset/[email protected]?part=12
> >
>
