Commit 0c2c7c06 authored by Peter Gonda's avatar Peter Gonda Committed by Paolo Bonzini
Browse files

KVM: SEV: Mark nested locking of vcpu->lock 



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: b5663931 ("KVM: SEV: Add support for SEV intra host migration")
Reported-by: default avatarJohn <Sperbeck&lt;jsperbeck@google.com>
Suggested-by: default avatarDavid Rientjes <rientjes@google.com>
Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Suggested-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: default avatarPeter Gonda <pgonda@google.com>

Message-Id: <20220502165807.529624-1-pgonda@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 04144108

arch/x86/kvm/svm/sev.c

+38 −4
Original line number Diff line number Diff line
@@ -1594,24 +1594,51 @@ 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;
@@ -1621,8 +1648,15 @@ 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);

	}

}
@@ -1748,10 +1782,10 @@ int sev_vm_move_enc_context_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;