kvm: arm64: Add helper for loading the stage2 setting for a VM

We load the stage2 context of a guest for different operations,
including running the guest and tlb maintenance on behalf of the
guest. As of now only the vttbr is private to the guest, but this
is about to change with IPA per VM. Add a helper to load the stage2
configuration for a VM, which could do the right thing with the
future changes.

Cc: Christoffer Dall <cdall@kernel.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/hyp/tlb.c

@@ -30,7 +30,7 @@ static void __hyp_text __tlb_switch_to_guest_vhe(struct kvm *kvm)
 	 * bits. Changing E2H is impossible (goodbye TTBR1_EL2), so
 	 * let's flip TGE before executing the TLB operation.
 	 */
-	write_sysreg(kvm->arch.vttbr, vttbr_el2);
+	__load_guest_stage2(kvm);
 	val = read_sysreg(hcr_el2);
 	val &= ~HCR_TGE;
 	write_sysreg(val, hcr_el2);
@@ -39,7 +39,7 @@ static void __hyp_text __tlb_switch_to_guest_vhe(struct kvm *kvm)
 
 static void __hyp_text __tlb_switch_to_guest_nvhe(struct kvm *kvm)
 {
-	write_sysreg(kvm->arch.vttbr, vttbr_el2);
+	__load_guest_stage2(kvm);
 	isb();
 }