[PATCH v4 5/9] KVM: arm64: Decouple hyp VM creation state from its handle

[Fuad Tabba]

Currently, the presence of a pKVM handle (pkvm.handle != 0) is used to
determine if the corresponding hypervisor (EL2) VM has been created and
initialized. This couples the handle's lifecycle with the VM's creation
state.

This coupling will become problematic with upcoming changes that will
allocate the pKVM handle earlier in the VM's life, before the VM is
instantiated at the hypervisor.

To prepare for this and make the state tracking explicit, decouple the
two concepts. Introduce a new boolean flag, 'pkvm.is_created', to track
whether the hypervisor-side VM has been created and initialized.

A new helper, pkvm_hyp_vm_is_created(), is added to check this flag. All
call sites that previously checked for the handle's existence are
converted to use the new, explicit check. The 'is_created' flag is set
to true upon successful creation in the hypervisor (EL2) and cleared
upon destruction.

Signed-off-by: Fuad Tabba <tabba at google.com>
---
 arch/arm64/include/asm/kvm_host.h |  1 +
 arch/arm64/include/asm/kvm_pkvm.h |  1 +
 arch/arm64/kvm/hyp/nvhe/pkvm.c    |  1 +
 arch/arm64/kvm/pkvm.c             | 11 +++++++++--
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7ad997dabddb..8ede884f091d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -253,6 +253,7 @@ struct kvm_protected_vm {
 	struct kvm_hyp_memcache teardown_mc;
 	struct kvm_hyp_memcache stage2_teardown_mc;
 	bool is_protected;
+	bool is_created;
 };
 
 struct kvm_mpidr_data {
diff --git a/arch/arm64/include/asm/kvm_pkvm.h b/arch/arm64/include/asm/kvm_pkvm.h
index 35f9d9478004..0aecd4ac5f45 100644
--- a/arch/arm64/include/asm/kvm_pkvm.h
+++ b/arch/arm64/include/asm/kvm_pkvm.h
@@ -18,6 +18,7 @@
 
 int pkvm_init_host_vm(struct kvm *kvm);
 int pkvm_create_hyp_vm(struct kvm *kvm);
+bool pkvm_hyp_vm_is_created(struct kvm *kvm);
 void pkvm_destroy_hyp_vm(struct kvm *kvm);
 int pkvm_create_hyp_vcpu(struct kvm_vcpu *vcpu);
 
diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c
index abe173406c88..969f6b293234 100644
--- a/arch/arm64/kvm/hyp/nvhe/pkvm.c
+++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c
@@ -407,6 +407,7 @@ static void init_pkvm_hyp_vm(struct kvm *host_kvm, struct pkvm_hyp_vm *hyp_vm,
 	hyp_vm->kvm.created_vcpus = nr_vcpus;
 	hyp_vm->kvm.arch.mmu.vtcr = host_mmu.arch.mmu.vtcr;
 	hyp_vm->kvm.arch.pkvm.is_protected = READ_ONCE(host_kvm->arch.pkvm.is_protected);
+	hyp_vm->kvm.arch.pkvm.is_created = true;
 	hyp_vm->kvm.arch.flags = 0;
 	pkvm_init_features_from_host(hyp_vm, host_kvm);
 }
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index 358168572482..2138dbfcb04b 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -87,12 +87,13 @@ void __init kvm_hyp_reserve(void)
 
 static void __pkvm_destroy_hyp_vm(struct kvm *kvm)
 {
-	if (kvm->arch.pkvm.handle) {
+	if (pkvm_hyp_vm_is_created(kvm)) {
 		WARN_ON(kvm_call_hyp_nvhe(__pkvm_teardown_vm,
 					  kvm->arch.pkvm.handle));
 	}
 
 	kvm->arch.pkvm.handle = 0;
+	kvm->arch.pkvm.is_created = false;
 	free_hyp_memcache(&kvm->arch.pkvm.teardown_mc);
 	free_hyp_memcache(&kvm->arch.pkvm.stage2_teardown_mc);
 }
@@ -165,6 +166,7 @@ static int __pkvm_create_hyp_vm(struct kvm *kvm)
 		goto free_vm;
 
 	kvm->arch.pkvm.handle = ret;
+	kvm->arch.pkvm.is_created = true;
 	kvm->arch.pkvm.stage2_teardown_mc.flags |= HYP_MEMCACHE_ACCOUNT_STAGE2;
 	kvm_account_pgtable_pages(pgd, pgd_sz / PAGE_SIZE);
 
@@ -176,12 +178,17 @@ static int __pkvm_create_hyp_vm(struct kvm *kvm)
 	return ret;
 }
 
+bool pkvm_hyp_vm_is_created(struct kvm *kvm)
+{
+	return READ_ONCE(kvm->arch.pkvm.is_created);
+}
+
 int pkvm_create_hyp_vm(struct kvm *kvm)
 {
 	int ret = 0;
 
 	mutex_lock(&kvm->arch.config_lock);
-	if (!kvm->arch.pkvm.handle)
+	if (!pkvm_hyp_vm_is_created(kvm))
 		ret = __pkvm_create_hyp_vm(kvm);
 	mutex_unlock(&kvm->arch.config_lock);
 
-- 
2.51.0.384.g4c02a37b29-goog