KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command

The command is used for copying the incoming buffer 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: 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
Reviewed-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Message-Id: <c5d0e3e719db7bb37ea85d79ed4db52e9da06257.1618498113.git.ashish.kalra@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Documentation/virt/kvm/amd-memory-encryption.rst

@@ -394,6 +394,30 @@ On success, the 'handle' field contains a new handle and on error, a negative va
 
 For more details, see SEV spec Section 6.12.
 
+16. KVM_SEV_RECEIVE_UPDATE_DATA
+----------------------------
+
+The KVM_SEV_RECEIVE_UPDATE_DATA command can be used by the hypervisor to copy
+the incoming buffers into the guest memory region with encryption context
+created during the KVM_SEV_RECEIVE_START.
+
+Parameters (in): struct kvm_sev_receive_update_data
+
+Returns: 0 on success, -negative on error
+
+::
+
+        struct kvm_sev_launch_receive_update_data {
+                __u64 hdr_uaddr;        /* userspace address containing the packet header */
+                __u32 hdr_len;
+
+                __u64 guest_uaddr;      /* the destination guest memory region */
+                __u32 guest_len;
+
+                __u64 trans_uaddr;      /* the incoming buffer memory region  */
+                __u32 trans_len;
+        };
+
 References
 ==========
 

arch/x86/kvm/svm/sev.c

@@ -1475,6 +1475,82 @@ static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct kvm_sev_receive_update_data params;
+	struct sev_data_receive_update_data *data;
+	void *hdr = NULL, *trans = NULL;
+	struct page **guest_page;
+	unsigned long n;
+	int ret, offset;
+
+	if (!sev_guest(kvm))
+		return -EINVAL;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+			sizeof(struct kvm_sev_receive_update_data)))
+		return -EFAULT;
+
+	if (!params.hdr_uaddr || !params.hdr_len ||
+	    !params.guest_uaddr || !params.guest_len ||
+	    !params.trans_uaddr || !params.trans_len)
+		return -EINVAL;
+
+	/* Check if we are crossing the page boundary */
+	offset = params.guest_uaddr & (PAGE_SIZE - 1);
+	if ((params.guest_len + offset > PAGE_SIZE))
+		return -EINVAL;
+
+	hdr = psp_copy_user_blob(params.hdr_uaddr, params.hdr_len);
+	if (IS_ERR(hdr))
+		return PTR_ERR(hdr);
+
+	trans = psp_copy_user_blob(params.trans_uaddr, params.trans_len);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto e_free_hdr;
+	}
+
+	ret = -ENOMEM;
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		goto e_free_trans;
+
+	data->hdr_address = __psp_pa(hdr);
+	data->hdr_len = params.hdr_len;
+	data->trans_address = __psp_pa(trans);
+	data->trans_len = params.trans_len;
+
+	/* Pin guest memory */
+	ret = -EFAULT;
+	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
+				    PAGE_SIZE, &n, 0);
+	if (!guest_page)
+		goto e_free;
+
+	/* The RECEIVE_UPDATE_DATA command requires C-bit to be always set. */
+	data->guest_address = (page_to_pfn(guest_page[0]) << PAGE_SHIFT) +
+				offset;
+	data->guest_address |= sev_me_mask;
+	data->guest_len = params.guest_len;
+	data->handle = sev->handle;
+
+	ret = sev_issue_cmd(kvm, SEV_CMD_RECEIVE_UPDATE_DATA, data,
+				&argp->error);
+
+	sev_unpin_memory(kvm, guest_page, n);
+
+e_free:
+	kfree(data);
+e_free_trans:
+	kfree(trans);
+e_free_hdr:
+	kfree(hdr);
+
+	return ret;
+}
+
 int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -1552,6 +1628,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_RECEIVE_START:
 		r = sev_receive_start(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_RECEIVE_UPDATE_DATA:
+		r = sev_receive_update_data(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;

include/uapi/linux/kvm.h

@@ -1764,6 +1764,15 @@ struct kvm_sev_receive_start {
 	__u32 session_len;
 };
 
+struct kvm_sev_receive_update_data {
+	__u64 hdr_uaddr;
+	__u32 hdr_len;
+	__u64 guest_uaddr;
+	__u32 guest_len;
+	__u64 trans_uaddr;
+	__u32 trans_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)