KVM: arm/arm64: vgic: Handle GICR_PENDBASER.PTZ filed as RAZ

Although guest will hardly read and use the PTZ (Pending Table Zero)
bit in GICR_PENDBASER, let us emulate the architecture strictly.
As per IHI 0069E 9.11.30, PTZ field is WO, and reads as 0.

Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20191220111833.1422-1-yuzenghui@huawei.com

virt/kvm/arm/vgic/vgic-mmio-v3.c

@@ -414,8 +414,11 @@ static unsigned long vgic_mmio_read_pendbase(struct kvm_vcpu *vcpu,
 					     gpa_t addr, unsigned int len)
 {
 	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+	u64 value = vgic_cpu->pendbaser;
 
-	return extract_bytes(vgic_cpu->pendbaser, addr & 7, len);
+	value &= ~GICR_PENDBASER_PTZ;
+
+	return extract_bytes(value, addr & 7, len);
 }
 
 static void vgic_mmio_write_pendbase(struct kvm_vcpu *vcpu,