RISC-V: KVM: Add ONE_REG interface for mvendorid, marchid, and mimpid

We add ONE_REG interface for VCPU mvendorid, marchid, and mimpid
so that KVM user-space can change this details to support migration
across heterogeneous hosts.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

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

@@ -49,6 +49,9 @@ struct kvm_sregs {
 struct kvm_riscv_config {
 	unsigned long isa;
 	unsigned long zicbom_block_size;
+	unsigned long mvendorid;
+	unsigned long marchid;
+	unsigned long mimpid;
 };
 
 /* CORE registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */

arch/riscv/kvm/vcpu.c

@@ -276,6 +276,15 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
 			return -EINVAL;
 		reg_val = riscv_cbom_block_size;
 		break;
+	case KVM_REG_RISCV_CONFIG_REG(mvendorid):
+		reg_val = vcpu->arch.mvendorid;
+		break;
+	case KVM_REG_RISCV_CONFIG_REG(marchid):
+		reg_val = vcpu->arch.marchid;
+		break;
+	case KVM_REG_RISCV_CONFIG_REG(mimpid):
+		reg_val = vcpu->arch.mimpid;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -338,6 +347,24 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 		break;
 	case KVM_REG_RISCV_CONFIG_REG(zicbom_block_size):
 		return -EOPNOTSUPP;
+	case KVM_REG_RISCV_CONFIG_REG(mvendorid):
+		if (!vcpu->arch.ran_atleast_once)
+			vcpu->arch.mvendorid = reg_val;
+		else
+			return -EBUSY;
+		break;
+	case KVM_REG_RISCV_CONFIG_REG(marchid):
+		if (!vcpu->arch.ran_atleast_once)
+			vcpu->arch.marchid = reg_val;
+		else
+			return -EBUSY;
+		break;
+	case KVM_REG_RISCV_CONFIG_REG(mimpid):
+		if (!vcpu->arch.ran_atleast_once)
+			vcpu->arch.mimpid = reg_val;
+		else
+			return -EBUSY;
+		break;
 	default:
 		return -EINVAL;
 	}