From: Peter Gonda <pgonda@xxxxxxxxxx>
[ Upstream commit 0c2c7c069285374fc8feacddc0498f8ab7627117 ]
svm_vm_migrate_from() uses sev_lock_vcpus_for_migration() to lock all
source and target vcpu->locks. Unfortunately there is an 8 subclass
limit, so a new subclass cannot be used for each vCPU. Instead maintain
ownership of the first vcpu's mutex.dep_map using a role specific
subclass: source vs target. Release the other vcpu's mutex.dep_maps.
Fixes: b56639318bb2b ("KVM: SEV: Add support for SEV intra host migration")
Reported-by: John Sperbeck<jsperbeck@xxxxxxxxxx>
Suggested-by: David Rientjes <rientjes@xxxxxxxxxx>
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
Message-Id: <20220502165807.529624-1-pgonda@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/x86/kvm/svm/sev.c | 42 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e5cecd4ad2d4..76e6411d4dde 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1590,24 +1590,51 @@ 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)
+static int sev_lock_vcpus_for_migration(struct kvm *kvm,
+ enum sev_migration_role role)
{
struct kvm_vcpu *vcpu;
unsigned long i, j;
+ bool first = true;
kvm_for_each_vcpu(i, vcpu, kvm) {
- if (mutex_lock_killable(&vcpu->mutex))
+ if (mutex_lock_killable_nested(&vcpu->mutex, role))
goto out_unlock;
+
+ if (first) {
+ /*
+ * Reset the role to one that avoids colliding with
+ * the role used for the first vcpu mutex.
+ */
+ role = SEV_NR_MIGRATION_ROLES;
+ first = false;
+ } else {
+ mutex_release(&vcpu->mutex.dep_map, _THIS_IP_);
+ }
}
return 0;
out_unlock:
+
+ first = true;
kvm_for_each_vcpu(j, vcpu, kvm) {
if (i == j)
break;
+ if (first)
+ first = false;
+ else
+ mutex_acquire(&vcpu->mutex.dep_map, role, 0, _THIS_IP_);
+
+
mutex_unlock(&vcpu->mutex);
}
return -EINTR;
@@ -1617,8 +1644,15 @@ 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);
}
}
@@ -1726,10 +1760,10 @@ int svm_vm_migrate_from(struct kvm *kvm, unsigned int source_fd)
charged = true;
}
- ret = sev_lock_vcpus_for_migration(kvm);
+ ret = sev_lock_vcpus_for_migration(kvm, SEV_MIGRATION_SOURCE);
if (ret)
goto out_dst_cgroup;
- ret = sev_lock_vcpus_for_migration(source_kvm);
+ ret = sev_lock_vcpus_for_migration(source_kvm, SEV_MIGRATION_TARGET);
if (ret)
goto out_dst_vcpu;
--
2.35.1
