KVM: Ensure all vcpus are consistent with in-kernel irqchip settings

(cherry picked from commit 3e515705a1f46beb1c942bb8043c16f8ac7b1e9e)

If some vcpus are created before KVM_CREATE_IRQCHIP, then
irqchip_in_kernel() and vcpu->arch.apic will be inconsistent, leading
to potential NULL pointer dereferences.

Fix by:
- ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
- ensuring that a vcpu has an apic if it is installed after KVM_CREATE_IRQCHIP

This is somewhat long winded because vcpu->arch.apic is created without
kvm->lock held.

Based on earlier patch by Michael Ellerman.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
static int vti_init_vpd(struct kvm_vcpu *vcpu)
{
	int i;
	union cpuid3_t cpuid3;
	struct vpd *vpd = to_host(vcpu->kvm, vcpu->arch.vpd);

	if (IS_ERR(vpd))
		return PTR_ERR(vpd);

	/* CPUID init */
	for (i = 0; i < 5; i++)
		vpd->vcpuid[i] = ia64_get_cpuid(i);

	/* Limit the CPUID number to 5 */
	cpuid3.value = vpd->vcpuid[3];
	cpuid3.number = 4;	/* 5 - 1 */
	vpd->vcpuid[3] = cpuid3.value;

	/*Set vac and vdc fields*/
	vpd->vac.a_from_int_cr = 1;
	vpd->vac.a_to_int_cr = 1;
	vpd->vac.a_from_psr = 1;
	vpd->vac.a_from_cpuid = 1;
	vpd->vac.a_cover = 1;
	vpd->vac.a_bsw = 1;
	vpd->vac.a_int = 1;
	vpd->vdc.d_vmsw = 1;

	/*Set virtual buffer*/
	vpd->virt_env_vaddr = KVM_VM_BUFFER_BASE;

	return 0;
}

static int vti_init_vpd(struct kvm_vcpu *vcpu)
{
	int i;
	union cpuid3_t cpuid3;
	struct vpd *vpd = to_host(vcpu->kvm, vcpu->arch.vpd);

	if (IS_ERR(vpd))
		return PTR_ERR(vpd);

	/* CPUID init */
	for (i = 0; i < 5; i++)
		vpd->vcpuid[i] = ia64_get_cpuid(i);

	/* Limit the CPUID number to 5 */
	cpuid3.value = vpd->vcpuid[3];
	cpuid3.number = 4;	/* 5 - 1 */
	vpd->vcpuid[3] = cpuid3.value;

	/*Set vac and vdc fields*/
	vpd->vac.a_from_int_cr = 1;
	vpd->vac.a_to_int_cr = 1;
	vpd->vac.a_from_psr = 1;
	vpd->vac.a_from_cpuid = 1;
	vpd->vac.a_cover = 1;
	vpd->vac.a_bsw = 1;
	vpd->vac.a_int = 1;
	vpd->vdc.d_vmsw = 1;

	/*Set virtual buffer*/
	vpd->virt_env_vaddr = KVM_VM_BUFFER_BASE;

	return 0;
}
