Drivers: hv: Support confidential VMBus channels

To make use of Confidential VMBus channels, initialize the
co_ring_buffers and co_external_memory fields of the channel
structure.

Advertise support upon negotiating the version and compute
values for those fields and initialize them.

Signed-off-by: Roman Kisel <[e-mail]>
Reviewed-by: Michael Kelley <[e-mail]>
Signed-off-by: Wei Liu <[e-mail]>

drivers/hv/channel_mgmt.c

···
 	struct vmbus_channel_offer_channel *offer;
 	struct vmbus_channel *oldchannel, *newchannel;
 	size_t offer_sz;
+	bool co_ring_buffer, co_external_memory;
 
 	offer = (struct vmbus_channel_offer_channel *)hdr;
 
···
 				   offer->child_relid);
 		atomic_dec(&vmbus_connection.offer_in_progress);
 		return;
+	}
+
+	co_ring_buffer = is_co_ring_buffer(offer);
+	co_external_memory = is_co_external_memory(offer);
+	if (!co_ring_buffer && co_external_memory) {
+		pr_err("Invalid offer relid=%d: the ring buffer isn't encrypted\n",
+			offer->child_relid);
+		return;
+	}
+	if (co_ring_buffer || co_external_memory) {
+		if (vmbus_proto_version < VERSION_WIN10_V6_0 || !vmbus_is_confidential()) {
+			pr_err("Invalid offer relid=%d: no support for confidential VMBus\n",
+				offer->child_relid);
+			atomic_dec(&vmbus_connection.offer_in_progress);
+			return;
+		}
 	}
 
 	oldchannel = find_primary_channel_by_offer(offer);
···
 		pr_err("Unable to allocate channel object\n");
 		return;
 	}
+	newchannel->co_ring_buffer = co_ring_buffer;
+	newchannel->co_external_memory = co_external_memory;
 
 	vmbus_setup_channel_state(newchannel, offer);
 

drivers/hv/connection.c

···
 		vmbus_connection.msg_conn_id = VMBUS_MESSAGE_CONNECTION_ID;
 	}
 
+	if (vmbus_is_confidential() && version >= VERSION_WIN10_V6_0)
+		msg->feature_flags = VMBUS_FEATURE_FLAG_CONFIDENTIAL_CHANNELS;
+
 	/*
 	 * shared_gpa_boundary is zero in non-SNP VMs, so it's safe to always
 	 * bitwise OR it