KVM: arm64: vgic-v3: Simplify vgic_v3_has_cpu_sysregs_attr()

Finding out whether a sysreg exists has little to do with that
register being accessed, so drop the is_write parameter.

Also, the reg pointer is completely unused, and we're better off
just passing the attr pointer to the function.

This result in a small cleanup of the calling site, with a new
helper converting the vGIC view of a sysreg into the canonical
one (this is purely cosmetic, as the encoding is the same).
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/vgic-sys-reg-v3.c

@@ -260,12 +260,18 @@ static const struct sys_reg_desc gic_v3_icc_reg_descs[] = {
 	{ SYS_DESC(SYS_ICC_IGRPEN1_EL1), access_gic_grpen1 },
 };
 
-int vgic_v3_has_cpu_sysregs_attr(struct kvm_vcpu *vcpu, bool is_write, u64 id,
-				u64 *reg)
+static u64 attr_to_id(u64 attr)
 {
-	u64 sysreg = (id & KVM_DEV_ARM_VGIC_SYSREG_MASK) | KVM_REG_SIZE_U64;
+	return ARM64_SYS_REG(FIELD_GET(KVM_REG_ARM_VGIC_SYSREG_OP0_MASK, attr),
+			     FIELD_GET(KVM_REG_ARM_VGIC_SYSREG_OP1_MASK, attr),
+			     FIELD_GET(KVM_REG_ARM_VGIC_SYSREG_CRN_MASK, attr),
+			     FIELD_GET(KVM_REG_ARM_VGIC_SYSREG_CRM_MASK, attr),
+			     FIELD_GET(KVM_REG_ARM_VGIC_SYSREG_OP2_MASK, attr));
+}
 
-	if (get_reg_by_id(sysreg, gic_v3_icc_reg_descs,
+int vgic_v3_has_cpu_sysregs_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
+{
+	if (get_reg_by_id(attr_to_id(attr->attr), gic_v3_icc_reg_descs,
 			  ARRAY_SIZE(gic_v3_icc_reg_descs)))
 		return 0;
 

arch/arm64/kvm/vgic/vgic-mmio-v3.c

@@ -986,12 +986,8 @@ int vgic_v3_has_attr_regs(struct kvm_device *dev, struct kvm_device_attr *attr)
 		iodev.base_addr = 0;
 		break;
 	}
-	case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS: {
-		u64 reg, id;
-
-		id = (attr->attr & KVM_DEV_ARM_VGIC_SYSREG_INSTR_MASK);
-		return vgic_v3_has_cpu_sysregs_attr(vcpu, 0, id, &reg);
-	}
+	case KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS:
+		return vgic_v3_has_cpu_sysregs_attr(vcpu, attr);
 	default:
 		return -ENXIO;
 	}

arch/arm64/kvm/vgic/vgic.h

@@ -247,8 +247,7 @@ int vgic_v3_redist_uaccess(struct kvm_vcpu *vcpu, bool is_write,
 			 int offset, u32 *val);
 int vgic_v3_cpu_sysregs_uaccess(struct kvm_vcpu *vcpu, bool is_write,
 			 u64 id, u64 *val);
-int vgic_v3_has_cpu_sysregs_attr(struct kvm_vcpu *vcpu, bool is_write, u64 id,
-				u64 *reg);
+int vgic_v3_has_cpu_sysregs_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 int vgic_v3_line_level_info_uaccess(struct kvm_vcpu *vcpu, bool is_write,
 				    u32 intid, u64 *val);
 int kvm_register_vgic_device(unsigned long type);