KVM: arm/arm64: Revisit Redistributor TYPER last bit computation

The TYPER of an redistributor reflects whether the rdist is
the last one of the redistributor region. Let's compare the TYPER
GPA against the address of the last occupied slot within the
redistributor region.
Signed-off-by: NEric Auger <eric.auger@redhat.com>
Reviewed-by: NChristoffer Dall <christoffer.dall@arm.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

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

@@ -184,12 +184,17 @@ static unsigned long vgic_mmio_read_v3r_typer(struct kvm_vcpu *vcpu,
 					      gpa_t addr, unsigned int len)
 {
 	unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu);
+	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+	struct vgic_redist_region *rdreg = vgic_cpu->rdreg;
 	int target_vcpu_id = vcpu->vcpu_id;
+	gpa_t last_rdist_typer = rdreg->base + GICR_TYPER +
+			(rdreg->free_index - 1) * KVM_VGIC_V3_REDIST_SIZE;
 	u64 value;
 
 	value = (u64)(mpidr & GENMASK(23, 0)) << 32;
 	value |= ((target_vcpu_id & 0xffff) << 8);
-	if (target_vcpu_id == atomic_read(&vcpu->kvm->online_vcpus) - 1)
+
+	if (addr == last_rdist_typer)
 		value |= GICR_TYPER_LAST;
 	if (vgic_has_its(vcpu->kvm))
 		value |= GICR_TYPER_PLPIS;