RISC-V: KVM: Implement subtype for CSR ONE_REG interface

To make the CSR ONE_REG interface extensible, we implement subtype
for the CSR ONE_REG IDs. The existing CSR ONE_REG IDs are treated
as subtype = 0 (aka General CSRs).
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/uapi/asm/kvm.h

@@ -65,7 +65,7 @@ struct kvm_riscv_core {
 #define KVM_RISCV_MODE_S	1
 #define KVM_RISCV_MODE_U	0
 
-/* CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
+/* General CSR registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */
 struct kvm_riscv_csr {
 	unsigned long sstatus;
 	unsigned long sie;
@@ -152,6 +152,7 @@ enum KVM_RISCV_SBI_EXT_ID {
 
 /* Control and status registers are mapped as type 3 */
 #define KVM_REG_RISCV_CSR		(0x03 << KVM_REG_RISCV_TYPE_SHIFT)
+#define KVM_REG_RISCV_CSR_GENERAL	(0x0 << KVM_REG_RISCV_SUBTYPE_SHIFT)
 #define KVM_REG_RISCV_CSR_REG(name)	\
 		(offsetof(struct kvm_riscv_csr, name) / sizeof(unsigned long))
 

arch/riscv/kvm/vcpu.c

@@ -460,27 +460,72 @@ static int kvm_riscv_vcpu_set_reg_core(struct kvm_vcpu *vcpu,
 	return 0;
 }
 
+static int kvm_riscv_vcpu_general_get_csr(struct kvm_vcpu *vcpu,
+					  unsigned long reg_num,
+					  unsigned long *out_val)
+{
+	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+
+	if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
+		return -EINVAL;
+
+	if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
+		kvm_riscv_vcpu_flush_interrupts(vcpu);
+		*out_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
+	} else
+		*out_val = ((unsigned long *)csr)[reg_num];
+
+	return 0;
+}
+
+static inline int kvm_riscv_vcpu_general_set_csr(struct kvm_vcpu *vcpu,
+						 unsigned long reg_num,
+						 unsigned long reg_val)
+{
+	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+
+	if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
+		return -EINVAL;
+
+	if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
+		reg_val &= VSIP_VALID_MASK;
+		reg_val <<= VSIP_TO_HVIP_SHIFT;
+	}
+
+	((unsigned long *)csr)[reg_num] = reg_val;
+
+	if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
+		WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
+
+	return 0;
+}
+
 static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
 				      const struct kvm_one_reg *reg)
 {
-	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+	int rc;
 	unsigned long __user *uaddr =
 			(unsigned long __user *)(unsigned long)reg->addr;
 	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
 					    KVM_REG_SIZE_MASK |
 					    KVM_REG_RISCV_CSR);
-	unsigned long reg_val;
+	unsigned long reg_val, reg_subtype;
 
 	if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
 		return -EINVAL;
-	if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
-		return -EINVAL;
 
-	if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
-		kvm_riscv_vcpu_flush_interrupts(vcpu);
-		reg_val = (csr->hvip >> VSIP_TO_HVIP_SHIFT) & VSIP_VALID_MASK;
-	} else
-		reg_val = ((unsigned long *)csr)[reg_num];
+	reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
+	reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
+	switch (reg_subtype) {
+	case KVM_REG_RISCV_CSR_GENERAL:
+		rc = kvm_riscv_vcpu_general_get_csr(vcpu, reg_num, &reg_val);
+		break;
+	default:
+		rc = -EINVAL;
+		break;
+	}
+	if (rc)
+		return rc;
 
 	if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;
@@ -491,31 +536,32 @@ static int kvm_riscv_vcpu_get_reg_csr(struct kvm_vcpu *vcpu,
 static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
 				      const struct kvm_one_reg *reg)
 {
-	struct kvm_vcpu_csr *csr = &vcpu->arch.guest_csr;
+	int rc;
 	unsigned long __user *uaddr =
 			(unsigned long __user *)(unsigned long)reg->addr;
 	unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
 					    KVM_REG_SIZE_MASK |
 					    KVM_REG_RISCV_CSR);
-	unsigned long reg_val;
+	unsigned long reg_val, reg_subtype;
 
 	if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
 		return -EINVAL;
-	if (reg_num >= sizeof(struct kvm_riscv_csr) / sizeof(unsigned long))
-		return -EINVAL;
 
 	if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
 		return -EFAULT;
 
-	if (reg_num == KVM_REG_RISCV_CSR_REG(sip)) {
-		reg_val &= VSIP_VALID_MASK;
-		reg_val <<= VSIP_TO_HVIP_SHIFT;
+	reg_subtype = reg_num & KVM_REG_RISCV_SUBTYPE_MASK;
+	reg_num &= ~KVM_REG_RISCV_SUBTYPE_MASK;
+	switch (reg_subtype) {
+	case KVM_REG_RISCV_CSR_GENERAL:
+		rc = kvm_riscv_vcpu_general_set_csr(vcpu, reg_num, reg_val);
+		break;
+	default:
+		rc = -EINVAL;
+		break;
 	}
-
-	((unsigned long *)csr)[reg_num] = reg_val;
-
-	if (reg_num == KVM_REG_RISCV_CSR_REG(sip))
-		WRITE_ONCE(vcpu->arch.irqs_pending_mask, 0);
+	if (rc)
+		return rc;
 
 	return 0;
 }