[PATCH] KVM: arm64: Fix circular locking dependency

[Oliver Upton]

On Tue, Jan 23, 2024 at 04:48:19PM +0000, Sebastian Ene wrote:
> The rule inside kvm enforces that the vcpu->mutex is taken *inside*
> kvm->lock. The rule is violated by the pkvm_create_hyp_vm which acquires
                                         ^~~~~~~~~~~~~~~~~~

nit: always suffix function names with '()'

> the kvm->lock while already holding the vcpu->mutex lock from
> kvm_vcpu_ioctl. Follow the rule by taking the config lock while getting the
> VM handle and make sure that this is cleaned on VM destroy under the
> same lock.

It is always better to describe a lock in terms of what data it
protects, the critical section(s) are rather obvious here.

  Avoid the circular locking dependency altogether by protecting the hyp
  vm handle with the config_lock, much like we already do for other
  forms of VM-scoped data.

> Signed-off-by: Sebastian Ene <sebastianene at google.com>
> Cc: stable at vger.kernel.org

nitpicks aside, this looks fine.

Reviewed-by: Oliver Upton <oliver.upton at linux.dev>

-- 
Thanks,
Oliver