arm64: KVM: Make ICC_SRE_EL1 access return the configured SRE value

When we trap ICC_SRE_EL1, we handle it as RAZ/WI. It would be
more correct to actual make it RO, and return the configured
value when read.
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm64/kvm/sys_regs.c

@@ -134,6 +134,17 @@ static bool access_gic_sgi(struct kvm_vcpu *vcpu,
 	return true;
 }
 
+static bool access_gic_sre(struct kvm_vcpu *vcpu,
+			   struct sys_reg_params *p,
+			   const struct sys_reg_desc *r)
+{
+	if (p->is_write)
+		return ignore_write(vcpu, p);
+
+	p->regval = vcpu->arch.vgic_cpu.vgic_v3.vgic_sre;
+	return true;
+}
+
 static bool trap_raz_wi(struct kvm_vcpu *vcpu,
 			struct sys_reg_params *p,
 			const struct sys_reg_desc *r)
@@ -958,7 +969,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	  access_gic_sgi },
 	/* ICC_SRE_EL1 */
 	{ Op0(0b11), Op1(0b000), CRn(0b1100), CRm(0b1100), Op2(0b101),
-	  trap_raz_wi },
+	  access_gic_sre },
 
 	/* CONTEXTIDR_EL1 */
 	{ Op0(0b11), Op1(0b000), CRn(0b1101), CRm(0b0000), Op2(0b001),