KVM: arm64: vgic-v3: Convert userspace accessors over to FIELD_GET/FIELD_PREP

The GICv3 userspace accessors are all about dealing with conversion
between fields from architectural registers and internal representations.

However, and owing to the age of this code, the accessors use
a combination of shift/mask that is hard to read. It is nonetheless
easy to make it better by using the FIELD_{GET,PREP} macros that solely
rely on a mask.

This results in somewhat nicer looking code, and is probably easier
to maintain.
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

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

@@ -23,30 +23,25 @@ static int set_gic_ctlr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	 * Disallow restoring VM state if not supported by this
 	 * hardware.
 	 */
-	host_pri_bits = ((val & ICC_CTLR_EL1_PRI_BITS_MASK) >>
-			 ICC_CTLR_EL1_PRI_BITS_SHIFT) + 1;
+	host_pri_bits = FIELD_GET(ICC_CTLR_EL1_PRI_BITS_MASK, val) + 1;
 	if (host_pri_bits > vgic_v3_cpu->num_pri_bits)
 		return -EINVAL;
 
 	vgic_v3_cpu->num_pri_bits = host_pri_bits;
 
-	host_id_bits = (val & ICC_CTLR_EL1_ID_BITS_MASK) >>
-		ICC_CTLR_EL1_ID_BITS_SHIFT;
+	host_id_bits = FIELD_GET(ICC_CTLR_EL1_ID_BITS_MASK, val);
 	if (host_id_bits > vgic_v3_cpu->num_id_bits)
 		return -EINVAL;
 
 	vgic_v3_cpu->num_id_bits = host_id_bits;
 
-	host_seis = ((kvm_vgic_global_state.ich_vtr_el2 &
-		      ICH_VTR_SEIS_MASK) >> ICH_VTR_SEIS_SHIFT);
-	seis = (val & ICC_CTLR_EL1_SEIS_MASK) >>
-		ICC_CTLR_EL1_SEIS_SHIFT;
+	host_seis = FIELD_GET(ICH_VTR_SEIS_MASK, kvm_vgic_global_state.ich_vtr_el2);
+	seis = FIELD_GET(ICC_CTLR_EL1_SEIS_MASK, val);
 	if (host_seis != seis)
 		return -EINVAL;
 
-	host_a3v = ((kvm_vgic_global_state.ich_vtr_el2 &
-		     ICH_VTR_A3V_MASK) >> ICH_VTR_A3V_SHIFT);
-	a3v = (val & ICC_CTLR_EL1_A3V_MASK) >> ICC_CTLR_EL1_A3V_SHIFT;
+	host_a3v = FIELD_GET(ICH_VTR_A3V_MASK, kvm_vgic_global_state.ich_vtr_el2);
+	a3v = FIELD_GET(ICC_CTLR_EL1_A3V_MASK, val);
 	if (host_a3v != a3v)
 		return -EINVAL;
 
@@ -54,8 +49,8 @@ static int set_gic_ctlr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	 * Here set VMCR.CTLR in ICC_CTLR_EL1 layout.
 	 * The vgic_set_vmcr() will convert to ICH_VMCR layout.
 	 */
-	vmcr.cbpr = (val & ICC_CTLR_EL1_CBPR_MASK) >> ICC_CTLR_EL1_CBPR_SHIFT;
-	vmcr.eoim = (val & ICC_CTLR_EL1_EOImode_MASK) >> ICC_CTLR_EL1_EOImode_SHIFT;
+	vmcr.cbpr = FIELD_GET(ICC_CTLR_EL1_CBPR_MASK, val);
+	vmcr.eoim = FIELD_GET(ICC_CTLR_EL1_EOImode_MASK, val);
 	vgic_set_vmcr(vcpu, &vmcr);
 
 	return 0;
@@ -70,20 +65,19 @@ static int get_gic_ctlr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 
 	vgic_get_vmcr(vcpu, &vmcr);
 	val = 0;
-	val |= (vgic_v3_cpu->num_pri_bits - 1) << ICC_CTLR_EL1_PRI_BITS_SHIFT;
-	val |= vgic_v3_cpu->num_id_bits << ICC_CTLR_EL1_ID_BITS_SHIFT;
-	val |= ((kvm_vgic_global_state.ich_vtr_el2 &
-		 ICH_VTR_SEIS_MASK) >> ICH_VTR_SEIS_SHIFT) <<
-		ICC_CTLR_EL1_SEIS_SHIFT;
-	val |= ((kvm_vgic_global_state.ich_vtr_el2 &
-		 ICH_VTR_A3V_MASK) >> ICH_VTR_A3V_SHIFT) <<
-		ICC_CTLR_EL1_A3V_SHIFT;
+	val |= FIELD_PREP(ICC_CTLR_EL1_PRI_BITS_MASK, vgic_v3_cpu->num_pri_bits - 1);
+	val |= FIELD_PREP(ICC_CTLR_EL1_ID_BITS_MASK, vgic_v3_cpu->num_id_bits);
+	val |= FIELD_PREP(ICC_CTLR_EL1_SEIS_MASK,
+			  FIELD_GET(ICH_VTR_SEIS_MASK,
+				    kvm_vgic_global_state.ich_vtr_el2));
+	val |= FIELD_PREP(ICC_CTLR_EL1_A3V_MASK,
+			  FIELD_GET(ICH_VTR_A3V_MASK, kvm_vgic_global_state.ich_vtr_el2));
 	/*
 	 * The VMCR.CTLR value is in ICC_CTLR_EL1 layout.
 	 * Extract it directly using ICC_CTLR_EL1 reg definitions.
 	 */
-	val |= (vmcr.cbpr << ICC_CTLR_EL1_CBPR_SHIFT) & ICC_CTLR_EL1_CBPR_MASK;
-	val |= (vmcr.eoim << ICC_CTLR_EL1_EOImode_SHIFT) & ICC_CTLR_EL1_EOImode_MASK;
+	val |= FIELD_PREP(ICC_CTLR_EL1_CBPR_MASK, vmcr.cbpr);
+	val |= FIELD_PREP(ICC_CTLR_EL1_EOImode_MASK, vmcr.eoim);
 
 	*valp = val;
 
@@ -96,7 +90,7 @@ static int set_gic_pmr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	vmcr.pmr = (val & ICC_PMR_EL1_MASK) >> ICC_PMR_EL1_SHIFT;
+	vmcr.pmr = FIELD_GET(ICC_PMR_EL1_MASK, val);
 	vgic_set_vmcr(vcpu, &vmcr);
 
 	return 0;
@@ -108,7 +102,7 @@ static int get_gic_pmr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	*val = (vmcr.pmr << ICC_PMR_EL1_SHIFT) & ICC_PMR_EL1_MASK;
+	*val = FIELD_PREP(ICC_PMR_EL1_MASK, vmcr.pmr);
 
 	return 0;
 }
@@ -119,7 +113,7 @@ static int set_gic_bpr0(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	vmcr.bpr = (val & ICC_BPR0_EL1_MASK) >> ICC_BPR0_EL1_SHIFT;
+	vmcr.bpr = FIELD_GET(ICC_BPR0_EL1_MASK, val);
 	vgic_set_vmcr(vcpu, &vmcr);
 
 	return 0;
@@ -131,7 +125,7 @@ static int get_gic_bpr0(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	*val = (vmcr.bpr << ICC_BPR0_EL1_SHIFT) & ICC_BPR0_EL1_MASK;
+	*val = FIELD_PREP(ICC_BPR0_EL1_MASK, vmcr.bpr);
 
 	return 0;
 }
@@ -143,7 +137,7 @@ static int set_gic_bpr1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 
 	vgic_get_vmcr(vcpu, &vmcr);
 	if (!vmcr.cbpr) {
-		vmcr.abpr = (val & ICC_BPR1_EL1_MASK) >> ICC_BPR1_EL1_SHIFT;
+		vmcr.abpr = FIELD_GET(ICC_BPR1_EL1_MASK, val);
 		vgic_set_vmcr(vcpu, &vmcr);
 	}
 
@@ -157,7 +151,7 @@ static int get_gic_bpr1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 
 	vgic_get_vmcr(vcpu, &vmcr);
 	if (!vmcr.cbpr)
-		*val = (vmcr.abpr << ICC_BPR1_EL1_SHIFT) & ICC_BPR1_EL1_MASK;
+		*val = FIELD_PREP(ICC_BPR1_EL1_MASK, vmcr.abpr);
 	else
 		*val = min((vmcr.bpr + 1), 7U);
 
@@ -171,7 +165,7 @@ static int set_gic_grpen0(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	vmcr.grpen0 = (val & ICC_IGRPEN0_EL1_MASK) >> ICC_IGRPEN0_EL1_SHIFT;
+	vmcr.grpen0 = FIELD_GET(ICC_IGRPEN0_EL1_MASK, val);
 	vgic_set_vmcr(vcpu, &vmcr);
 
 	return 0;
@@ -183,7 +177,7 @@ static int get_gic_grpen0(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	*val = (vmcr.grpen0 << ICC_IGRPEN0_EL1_SHIFT) & ICC_IGRPEN0_EL1_MASK;
+	*val = FIELD_PREP(ICC_IGRPEN0_EL1_MASK, vmcr.grpen0);
 
 	return 0;
 }
@@ -194,7 +188,7 @@ static int set_gic_grpen1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	vmcr.grpen1 = (val & ICC_IGRPEN1_EL1_MASK) >> ICC_IGRPEN1_EL1_SHIFT;
+	vmcr.grpen1 = FIELD_GET(ICC_IGRPEN1_EL1_MASK, val);
 	vgic_set_vmcr(vcpu, &vmcr);
 
 	return 0;
@@ -206,7 +200,7 @@ static int get_gic_grpen1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r,
 	struct vgic_vmcr vmcr;
 
 	vgic_get_vmcr(vcpu, &vmcr);
-	*val = (vmcr.grpen1 << ICC_IGRPEN1_EL1_SHIFT) & ICC_IGRPEN1_EL1_MASK;
+	*val = FIELD_GET(ICC_IGRPEN1_EL1_MASK, vmcr.grpen1);
 
 	return 0;
 }