commit f00327731131 ("KVM: arm64: Use config_lock to protect vgic state") was meant to rectify a longstanding lock ordering issue in KVM where the kvm->lock is taken while holding vcpu->mutex. As it so happens, the aforementioned commit introduced yet another locking issue by acquiring the its_lock before acquiring the config lock.

This is obviously wrong, especially considering that the lock ordering is well documented in vgic.c. Reshuffle the locks once more to take the config_lock before the its_lock. While at it, sprinkle in the lockdep hinting that has become popular as of late to keep lockdep apprised of our ordering.

Cc: stable@vger.kernel.org Fixes: f00327731131 ("KVM: arm64: Use config_lock to protect vgic state") Signed-off-by: Oliver Upton oliver.upton@linux.dev ---

Applies to kvmarm/next. Tested with QEMU with lockdep enabled.

arch/arm64/kvm/vgic/vgic-its.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/vgic/vgic-its.c b/arch/arm64/kvm/vgic/vgic-its.c index 7713cd06104e..750e51e3779a 100644 --- a/arch/arm64/kvm/vgic/vgic-its.c +++ b/arch/arm64/kvm/vgic/vgic-its.c @@ -1958,6 +1958,16 @@ static int vgic_its_create(struct kvm_device *dev, u32 type) mutex_init(&its->its_lock); mutex_init(&its->cmd_lock);

+ /* Yep, even more trickery for lock ordering... */ +#ifdef CONFIG_LOCKDEP + mutex_lock(&dev->kvm->arch.config_lock); + mutex_lock(&its->cmd_lock); + mutex_lock(&its->its_lock); + mutex_unlock(&its->its_lock); + mutex_unlock(&its->cmd_lock); + mutex_unlock(&dev->kvm->arch.config_lock); +#endif + its->vgic_its_base = VGIC_ADDR_UNDEF;

INIT_LIST_HEAD(&its->device_list); @@ -2752,15 +2762,14 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) return 0;

mutex_lock(&kvm->lock); - mutex_lock(&its->its_lock);

if (!lock_all_vcpus(kvm)) { - mutex_unlock(&its->its_lock); mutex_unlock(&kvm->lock); return -EBUSY; }

mutex_lock(&kvm->arch.config_lock); + mutex_lock(&its->its_lock);

switch (attr) { case KVM_DEV_ARM_ITS_CTRL_RESET: @@ -2774,9 +2783,9 @@ static int vgic_its_ctrl(struct kvm *kvm, struct vgic_its *its, u64 attr) break; }

+ mutex_unlock(&its->its_lock); mutex_unlock(&kvm->arch.config_lock); unlock_all_vcpus(kvm); - mutex_unlock(&its->its_lock); mutex_unlock(&kvm->lock); return ret; }

base-commit: df706d5176fdd92cdfe27ee6ec4389e4cff18bed