[RFC PATCH v2 04/11] KVM: SVM: Add support for KVM_SEV_RECEIVE_START command

["Singh, Brijesh" <brijesh.singh@amd.com>]

The command is used to create the encryption context for an incoming
SEV guest. The encryption context can be later used by the hypervisor
to import the incoming data into the SEV guest memory space.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 .../virtual/kvm/amd-memory-encryption.rst     | 29 +++++++
 arch/x86/kvm/svm.c                            | 80 +++++++++++++++++++
 include/uapi/linux/kvm.h                      |  9 +++
 3 files changed, 118 insertions(+)

diff --git a/Documentation/virtual/kvm/amd-memory-encryption.rst b/Documentation/virtual/kvm/amd-memory-encryption.rst
index afa11a7271f1..85abe0871031 100644
--- a/Documentation/virtual/kvm/amd-memory-encryption.rst
+++ b/Documentation/virtual/kvm/amd-memory-encryption.rst
@@ -297,6 +297,35 @@ issued by the hypervisor to delete the encryption context.
 
 Returns: 0 on success, -negative on error
 
+13. KVM_SEV_RECEIVE_START
+------------------------
+
+The KVM_SEV_RECEIVE_START command is used for creating the memory encryption
+context for an incoming SEV guest. To create the encryption context, the user must
+provide a guest policy, the platform public Diffie-Hellman (PDH) key and session
+information.
+
+Parameters: struct  kvm_sev_receive_start (in/out)
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_sev_receive_start {
+                __u32 handle;           /* if zero then firmware creates a new handle */
+                __u32 policy;           /* guest's policy */
+
+                __u64 pdh_uaddr;         /* userspace address pointing to the PDH key */
+                __u32 dh_len;
+
+                __u64 session_addr;     /* userspace address which points to the guest session information */
+                __u32 session_len;
+        };
+
+On success, the 'handle' field contains a new handle and on error, a negative value.
+
+For more details, see SEV spec Section 6.12.
+
 References
 ==========
 
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3dfe3f051dd9..94a55e4128aa 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7191,6 +7191,83 @@ static int sev_send_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct sev_data_receive_start *start;
+	struct kvm_sev_receive_start params;
+	int *error = &argp->error;
+	void *session_data = NULL;
+	void *pdh_data = NULL;
+	int ret;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	/* Get parameter from the user */
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			sizeof(struct kvm_sev_receive_start)))
+		return -EFAULT;
+
+	if (!params.pdh_uaddr || !params.pdh_len ||
+	    !params.session_uaddr || !params.session_len)
+		return -EINVAL;
+
+	start = kzalloc(sizeof(*start), GFP_KERNEL);
+	if (!start)
+		return -ENOMEM;
+
+	start->handle = params.handle;
+	start->policy = params.policy;
+
+	pdh_data = psp_copy_user_blob(params.pdh_uaddr, params.pdh_len);
+	if (IS_ERR(pdh_data)) {
+		ret = PTR_ERR(pdh_data);
+		goto e_free;
+	}
+
+	start->pdh_cert_address = __psp_pa(pdh_data);
+	start->pdh_cert_len = params.pdh_len;
+
+	session_data = psp_copy_user_blob(params.session_uaddr, params.session_len);
+	if (IS_ERR(session_data)) {
+		ret = PTR_ERR(session_data);
+		goto e_free_pdh;
+	}
+
+	start->session_address = __psp_pa(session_data);
+	start->session_len = params.session_len;
+
+	/* create memory encryption context */
+	ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_RECEIVE_START, start, error);
+	if (ret)
+		goto e_free_session;
+
+	/* Bind ASID to this guest */
+	ret = sev_bind_asid(kvm, start->handle, error);
+	if (ret)
+		goto e_free_session;
+
+	params.handle = start->handle;
+	if (copy_to_user((void __user *)(uintptr_t)argp->data,
+			 &params, sizeof(struct kvm_sev_receive_start))) {
+		ret = -EFAULT;
+		sev_unbind_asid(kvm, start->handle);
+		goto e_free_session;
+	}
+
+	sev->handle = start->handle;
+	sev->fd = argp->sev_fd;
+
+e_free_session:
+	kfree(session_data);
+e_free_pdh:
+	kfree(pdh_data);
+e_free:
+	kfree(start);
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -7241,6 +7318,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_SEND_FINISH:
 		r = sev_send_finish(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_RECEIVE_START:
+		r = sev_receive_start(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4cb6c3774ec2..28d240974ea7 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1552,6 +1552,15 @@ struct kvm_sev_send_update_data {
 	__u32 trans_len;
 };
 
+struct kvm_sev_receive_start {
+	__u32 handle;
+	__u32 policy;
+	__u64 pdh_uaddr;
+	__u32 pdh_len;
+	__u64 session_uaddr;
+	__u32 session_len;
+};
+
 #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
 #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
 #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)
-- 
2.17.1