ARM/ARM64: KVM: Implement KVM_ARM_PREFERRED_TARGET ioctl

For implementing CPU=host, we need a mechanism for querying
preferred VCPU target type on underlying Host.

This patch implements KVM_ARM_PREFERRED_TARGET vm ioctl which
returns struct kvm_vcpu_init instance containing information
about preferred VCPU target type and target specific features
available for it.

Signed-off-by: Anup Patel <anup.patel@linaro.org>
Signed-off-by: Pranavkumar Sawargaonkar <pranavkumar@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

2 files changed, 14 insertions, 0 deletions

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 9c697db2787e..cc5adb9349ef 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -797,6 +797,19 @@ long kvm_arch_vm_ioctl(struct file *filp,
                         return -EFAULT;
                 return kvm_vm_ioctl_set_device_addr(kvm, &dev_addr);
         }
+        case KVM_ARM_PREFERRED_TARGET: {
+                int err;
+                struct kvm_vcpu_init init;
+
+                err = kvm_vcpu_preferred_target(&init);
+                if (err)
+                        return err;
+
+                if (copy_to_user(argp, &init, sizeof(init)))
+                        return -EFAULT;
+
+                return 0;
+        }
         default:
                 return -EINVAL;
         }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 99c25338ede8..e32e776f20c0 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1012,6 +1012,7 @@ struct kvm_s390_ucas_mapping {
 /* VM is being stopped by host */
 #define KVM_KVMCLOCK_CTRL         _IO(KVMIO,   0xad)
 #define KVM_ARM_VCPU_INIT         _IOW(KVMIO,  0xae, struct kvm_vcpu_init)
+#define KVM_ARM_PREFERRED_TARGET  _IOR(KVMIO,  0xaf, struct kvm_vcpu_init)
 #define KVM_GET_REG_LIST          _IOWR(KVMIO, 0xb0, struct kvm_reg_list)
 
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU     (1 << 0)