KVM: arm64: Use config_lock to protect vgic state

Almost all of the vgic state is VM-scoped but accessed from the context
of a vCPU. These accesses were serialized on the kvm->lock which cannot
be nested within a vcpu->mutex critical section.

Move over the vgic state to using the config_lock. Tweak the lock
ordering where necessary to ensure that the config_lock is acquired
after the vcpu->mutex. Acquire the config_lock in kvm_vgic_create() to
avoid a race between the converted flows and GIC creation. Where
necessary, continue to acquire kvm->lock to avoid a race with vCPU
creation (i.e. flows that use lock_all_vcpus()).

Finally, promote the locking expectations in comments to lockdep
assertions and update the locking documentation for the config_lock as
well as vcpu->mutex.

Cc: stable@vger.kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230327164747.2466958-5-oliver.upton@linux.dev

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
index 91201f743033..472b18ac92a2 100644
--- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
@@ -111,7 +111,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
 	case GICD_CTLR: {
 		bool was_enabled, is_hwsgi;
 
-		mutex_lock(&vcpu->kvm->lock);
+		mutex_lock(&vcpu->kvm->arch.config_lock);
 
 		was_enabled = dist->enabled;
 		is_hwsgi = dist->nassgireq;
@@ -139,7 +139,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
 		else if (!was_enabled && dist->enabled)
 			vgic_kick_vcpus(vcpu->kvm);
 
-		mutex_unlock(&vcpu->kvm->lock);
+		mutex_unlock(&vcpu->kvm->arch.config_lock);
 		break;
 	}
 	case GICD_TYPER: