KVM: arm64: Move debug dirty flag calculation out of world switch

There is no need to figure out inside the world-switch if we should
save/restore the debug registers or not, we might as well do that in the
higher level debug setup code, making it easier to optimize down the
line.
Reviewed-by: NJulien Thierry <julien.thierry@arm.com>
Reviewed-by: NMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: NAndrew Jones <drjones@redhat.com>
Signed-off-by: NChristoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/debug.c

@@ -193,6 +193,11 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
 	if (trap_debug)
 		vcpu->arch.mdcr_el2 |= MDCR_EL2_TDA;
 
+	/* If KDE or MDE are set, perform a full save/restore cycle. */
+	if ((vcpu_sys_reg(vcpu, MDSCR_EL1) & DBG_MDSCR_KDE) ||
+	    (vcpu_sys_reg(vcpu, MDSCR_EL1) & DBG_MDSCR_MDE))
+		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
+
 	trace_kvm_arm_set_dreg32("MDCR_EL2", vcpu->arch.mdcr_el2);
 	trace_kvm_arm_set_dreg32("MDSCR_EL1", vcpu_sys_reg(vcpu, MDSCR_EL1));
 }

arch/arm64/kvm/hyp/debug-sr.c

@@ -166,12 +166,6 @@ void __hyp_text __debug_restore_state(struct kvm_vcpu *vcpu,
 
 void __hyp_text __debug_cond_save_host_state(struct kvm_vcpu *vcpu)
 {
-	/* If any of KDE, MDE or KVM_ARM64_DEBUG_DIRTY is set, perform
-	 * a full save/restore cycle. */
-	if ((vcpu->arch.ctxt.sys_regs[MDSCR_EL1] & DBG_MDSCR_KDE) ||
-	    (vcpu->arch.ctxt.sys_regs[MDSCR_EL1] & DBG_MDSCR_MDE))
-		vcpu->arch.debug_flags |= KVM_ARM64_DEBUG_DIRTY;
-
 	__debug_save_state(vcpu, &vcpu->arch.host_debug_state.regs,
 			   kern_hyp_va(vcpu->arch.host_cpu_context));
 	__debug_save_spe()(&vcpu->arch.host_debug_state.pmscr_el1);