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KVM: arm64: Prevent teardown finalisation of referenced 'hyp_vm'

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Destroying a 'hyp_vm' with an elevated referenced count in
__pkvm_finalize_teardown_vm() is only going to lead to tears.

In preparation for allowing limited references to be acquired on dying
VMs during the teardown process, factor out the handle-to-vm logic for
the teardown path and reuse it for both the 'start' and 'finalise'
stages of the teardown process.

Signed-off-by: Will Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260331155056.28220-2-will@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Will Deacon 2026-03-31 16:50:53 +01:00 committed by Marc Zyngier
parent 61135967fa
commit 760299a1d8
1 changed files with 18 additions and 14 deletions
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32
arch/arm64/kvm/hyp/nvhe/pkvm.c
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@ -936,20 +936,27 @@ int __pkvm_reclaim_dying_guest_page(pkvm_handle_t handle, u64 gfn)
return ret;
}
static struct pkvm_hyp_vm *get_pkvm_unref_hyp_vm_locked(pkvm_handle_t handle)
{
struct pkvm_hyp_vm *hyp_vm;
hyp_assert_lock_held(&vm_table_lock);
hyp_vm = get_vm_by_handle(handle);
if (!hyp_vm || hyp_page_count(hyp_vm))
return NULL;
return hyp_vm;
}
int __pkvm_start_teardown_vm(pkvm_handle_t handle)
{
struct pkvm_hyp_vm *hyp_vm;
int ret = 0;
hyp_spin_lock(&vm_table_lock);
hyp_vm = get_vm_by_handle(handle);
if (!hyp_vm) {
ret = -ENOENT;
goto unlock;
} else if (WARN_ON(hyp_page_count(hyp_vm))) {
ret = -EBUSY;
goto unlock;
} else if (hyp_vm->kvm.arch.pkvm.is_dying) {
hyp_vm = get_pkvm_unref_hyp_vm_locked(handle);
if (!hyp_vm || hyp_vm->kvm.arch.pkvm.is_dying) {
ret = -EINVAL;
goto unlock;
}
@ -971,12 +978,9 @@ int __pkvm_finalize_teardown_vm(pkvm_handle_t handle)
int err;
hyp_spin_lock(&vm_table_lock);
hyp_vm = get_vm_by_handle(handle);
if (!hyp_vm) {
err = -ENOENT;
goto err_unlock;
} else if (!hyp_vm->kvm.arch.pkvm.is_dying) {
err = -EBUSY;
hyp_vm = get_pkvm_unref_hyp_vm_locked(handle);
if (!hyp_vm || !hyp_vm->kvm.arch.pkvm.is_dying) {
err = -EINVAL;
goto err_unlock;
}