KVM: arm64: vgic: Don't check for vgic_ready() when setting NR_IRQS

KVM commits to a particular sizing of SPIs when the vgic is initialized,
which is before the point a vgic becomes ready. On top of that, KVM
supplies a default amount of SPIs should userspace not explicitly
configure this.

As such, the check for vgic_ready() in the handling of
KVM_DEV_ARM_VGIC_GRP_NR_IRQS is completely wrong, and testing if nr_spis
is nonzero is sufficient for preventing userspace from playing games
with us.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241017001947.2707312-2-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: oupton

arch/arm64/kvm/vgic/vgic-kvm-device.c

@@ -236,7 +236,12 @@ static int vgic_set_common_attr(struct kvm_device *dev,
 
 		mutex_lock(&dev->kvm->arch.config_lock);
 
-		if (vgic_ready(dev->kvm) || dev->kvm->arch.vgic.nr_spis)
+		/*
+		 * Either userspace has already configured NR_IRQS or
+		 * the vgic has already been initialized and vgic_init()
+		 * supplied a default amount of SPIs.
+		 */
+		if (dev->kvm->arch.vgic.nr_spis)
 			ret = -EBUSY;
 		else
 			dev->kvm->arch.vgic.nr_spis =