kvm: nVMX: Introduce KVM_CAP_NESTED_STATE

For nested virtualization L0 KVM is managing a bit of state for L2 guests,
this state can not be captured through the currently available IOCTLs. In
fact the state captured through all of these IOCTLs is usually a mix of L1
and L2 state. It is also dependent on whether the L2 guest was running at
the moment when the process was interrupted to save its state.

With this capability, there are two new vcpu ioctls: KVM_GET_NESTED_STATE
and KVM_SET_NESTED_STATE. These can be used for saving and restoring a VM
that is in VMX operation.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jim Mattson <jmattson@google.com>
[karahmed@ - rename structs and functions and make them ready for AMD and
             address previous comments.
           - handle nested.smm state.
           - rebase & a bit of refactoring.
           - Merge 7/8 and 8/8 into one patch. ]
Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fbd59ad047b0..1b14c4a654c3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2947,6 +2947,10 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_X2APIC_API:
 		r = KVM_X2APIC_API_VALID_FLAGS;
 		break;
+	case KVM_CAP_NESTED_STATE:
+		r = kvm_x86_ops->get_nested_state ?
+			kvm_x86_ops->get_nested_state(NULL, 0, 0) : 0;
+		break;
 	default:
 		break;
 	}
@@ -3963,6 +3967,56 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		r = kvm_vcpu_ioctl_enable_cap(vcpu, &cap);
 		break;
 	}
+	case KVM_GET_NESTED_STATE: {
+		struct kvm_nested_state __user *user_kvm_nested_state = argp;
+		u32 user_data_size;
+
+		r = -EINVAL;
+		if (!kvm_x86_ops->get_nested_state)
+			break;
+
+		BUILD_BUG_ON(sizeof(user_data_size) != sizeof(user_kvm_nested_state->size));
+		if (get_user(user_data_size, &user_kvm_nested_state->size))
+			return -EFAULT;
+
+		r = kvm_x86_ops->get_nested_state(vcpu, user_kvm_nested_state,
+						  user_data_size);
+		if (r < 0)
+			return r;
+
+		if (r > user_data_size) {
+			if (put_user(r, &user_kvm_nested_state->size))
+				return -EFAULT;
+			return -E2BIG;
+		}
+		r = 0;
+		break;
+	}
+	case KVM_SET_NESTED_STATE: {
+		struct kvm_nested_state __user *user_kvm_nested_state = argp;
+		struct kvm_nested_state kvm_state;
+
+		r = -EINVAL;
+		if (!kvm_x86_ops->set_nested_state)
+			break;
+
+		if (copy_from_user(&kvm_state, user_kvm_nested_state, sizeof(kvm_state)))
+			return -EFAULT;
+
+		if (kvm_state.size < sizeof(kvm_state))
+			return -EINVAL;
+
+		if (kvm_state.flags &
+		    ~(KVM_STATE_NESTED_RUN_PENDING | KVM_STATE_NESTED_GUEST_MODE))
+			return -EINVAL;
+
+		/* nested_run_pending implies guest_mode.  */
+		if (kvm_state.flags == KVM_STATE_NESTED_RUN_PENDING)
+			return -EINVAL;
+
+		r = kvm_x86_ops->set_nested_state(vcpu, user_kvm_nested_state, &kvm_state);
+		break;
+	}
 	default:
 		r = -EINVAL;
 	}