[PATCH v4 5/5] x86: KVM: SEV: implement kvm_lock_all_vcpus and use it

Maxim Levitsky
2025-04-30T20:31:01Z

Implement kvm_lock_all_vcpus() and use it instead of
sev own sev_{lock|unlock}_vcpus_for_migration().

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
arch/x86/kvm/svm/sev.c | 72 +++-------------------------------------
include/linux/kvm_host.h | 1 +
virt/kvm/kvm_main.c | 25 ++++++++++++++
3 files changed, 30 insertions(+), 68 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0bc708ee2788..16db6179013d 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1882,70 +1882,6 @@ static void sev_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
atomic_set_release(&src_sev->migration_in_progress, 0);
}

-/* vCPU mutex subclasses. */
-enum sev_migration_role {
- SEV_MIGRATION_SOURCE = 0,
- SEV_MIGRATION_TARGET,
- SEV_NR_MIGRATION_ROLES,
-};
-
-static int sev_lock_vcpus_for_migration(struct kvm *kvm,
- enum sev_migration_role role)
-{
- struct kvm_vcpu *vcpu;
- unsigned long i, j;
-
- kvm_for_each_vcpu(i, vcpu, kvm) {
- if (mutex_lock_killable_nested(&vcpu->mutex, role))
- goto out_unlock;
-
-#ifdef CONFIG_PROVE_LOCKING
- if (!i)
- /*
- * Reset the role to one that avoids colliding with
- * the role used for the first vcpu mutex.
- */
- role = SEV_NR_MIGRATION_ROLES;
- else
- mutex_release(&vcpu->mutex.dep_map, _THIS_IP_);
-#endif
- }
-
- return 0;
-
-out_unlock:
-
- kvm_for_each_vcpu(j, vcpu, kvm) {
- if (i == j)
- break;
-
-#ifdef CONFIG_PROVE_LOCKING
- if (j)
- mutex_acquire(&vcpu->mutex.dep_map, role, 0, _THIS_IP_);
-#endif
-
- mutex_unlock(&vcpu->mutex);
- }
- return -EINTR;
-}
-
-static void sev_unlock_vcpus_for_migration(struct kvm *kvm)
-{
- struct kvm_vcpu *vcpu;
- unsigned long i;
- bool first = true;
-
- kvm_for_each_vcpu(i, vcpu, kvm) {
- if (first)
- first = false;
- else
- mutex_acquire(&vcpu->mutex.dep_map,
- SEV_NR_MIGRATION_ROLES, 0, _THIS_IP_);
-
- mutex_unlock(&vcpu->mutex);
- }
-}
-
static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm)
{
struct kvm_sev_info *dst = to_kvm_sev_info(dst_kvm);
@@ -2083,10 +2019,10 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
charged = true;
}

- ret = sev_lock_vcpus_for_migration(kvm, SEV_MIGRATION_SOURCE);
+ ret = kvm_lock_all_vcpus(kvm);
if (ret)
goto out_dst_cgroup;
- ret = sev_lock_vcpus_for_migration(source_kvm, SEV_MIGRATION_TARGET);
+ ret = kvm_lock_all_vcpus(source_kvm);
if (ret)
goto out_dst_vcpu;

@@ -2100,9 +2036,9 @@ int sev_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
ret = 0;

out_source_vcpu:
- sev_unlock_vcpus_for_migration(source_kvm);
+ kvm_unlock_all_vcpus(source_kvm);
out_dst_vcpu:
- sev_unlock_vcpus_for_migration(kvm);
+ kvm_unlock_all_vcpus(kvm);
out_dst_cgroup:
/* Operates on the source on success, on the destination on failure. */
if (charged)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 10d6652c7aa0..a6140415c693 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1016,6 +1016,7 @@ static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
void kvm_destroy_vcpus(struct kvm *kvm);

int kvm_trylock_all_vcpus(struct kvm *kvm);
+int kvm_lock_all_vcpus(struct kvm *kvm);
void kvm_unlock_all_vcpus(struct kvm *kvm);

void vcpu_load(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 834f08dfa24c..9211b07b0565 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1392,6 +1392,31 @@ int kvm_trylock_all_vcpus(struct kvm *kvm)
}
EXPORT_SYMBOL_GPL(kvm_trylock_all_vcpus);

+/*
+ * Lock all of the VM's vCPUs.
+ * Assumes that the kvm->lock is held.
+ * Returns -EINTR if the process is killed.
+ */
+int kvm_lock_all_vcpus(struct kvm *kvm)
+{
+ struct kvm_vcpu *vcpu;
+ unsigned long i, j;
+
+ kvm_for_each_vcpu(i, vcpu, kvm)
+ if (mutex_lock_killable_nest_lock(&vcpu->mutex, &kvm->lock))
+ goto out_unlock;
+ return 0;
+
+out_unlock:
+ kvm_for_each_vcpu(j, vcpu, kvm) {
+ if (i == j)
+ break;
+ mutex_unlock(&vcpu->mutex);
+ }
+ return -EINTR;
+}
+EXPORT_SYMBOL_GPL(kvm_lock_all_vcpus);
+
void kvm_unlock_all_vcpus(struct kvm *kvm)
{
struct kvm_vcpu *vcpu;
--
2.46.0