[PATCH] KVM: arm64: Mark freed S2 MMUs as invalid

[PATCH] KVM: arm64: Mark freed S2 MMUs as invalid

[Marc Zyngier]

When freeing an S2 MMU, we free the associated pgd, but omit to
mark the structure as invalid. Subsequently, a call to
kvm_nested_s2_unmap() would pick these invalid S2 MMUs and
pass them down the teardown path.

This ends up with a nasty warning as we try to unmap an unallocated
set of page tables.

Fix this by making the S2 MMU invalid on freeing the pgd by calling
kvm_init_nested_s2_mmu().

Fixes: 4f128f8e1aaa ("KVM: arm64: nv: Support multiple nested Stage-2 mmu structures")
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/mmu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 9a45daf817bf..315aaadfda30 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -1074,6 +1074,10 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
 		mmu->pgt = NULL;
 		free_percpu(mmu->last_vcpu_ran);
 	}
+
+	if (kvm_is_nested_s2_mmu(kvm, mmu))
+		kvm_init_nested_s2_mmu(mmu);
+		
 	write_unlock(&kvm->mmu_lock);
 
 	if (pgt) {
-- 
2.47.2

Re: [PATCH] KVM: arm64: Mark freed S2 MMUs as invalid

[Oliver Upton]

On Fri, 05 Sep 2025 08:28:59 +0100, Marc Zyngier wrote:
> When freeing an S2 MMU, we free the associated pgd, but omit to
> mark the structure as invalid. Subsequently, a call to
> kvm_nested_s2_unmap() would pick these invalid S2 MMUs and
> pass them down the teardown path.
> 
> This ends up with a nasty warning as we try to unmap an unallocated
> set of page tables.
> 
> [...]

Applied to fixes, thanks!

[1/1] KVM: arm64: Mark freed S2 MMUs as invalid
      https://git.kernel.org/kvmarm/kvmarm/c/34b8f4adedd5

--
Best,
Oliver