From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:57581) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hBaNk-0006pz-RY for qemu-devel@nongnu.org; Wed, 03 Apr 2019 03:32:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hBaNj-0002b3-Sv for qemu-devel@nongnu.org; Wed, 03 Apr 2019 03:32:24 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:41438 helo=huawei.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hBaNj-0002Yl-FK for qemu-devel@nongnu.org; Wed, 03 Apr 2019 03:32:23 -0400 From: Heyi Guo Message-ID: Date: Wed, 3 Apr 2019 15:32:09 +0800 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Question: can we hot plug a PCIe switch on machine "virt" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Marcel Apfelbaum , "Michael S. Tsirkin" Cc: wanghaibin 00208455 Hi folks, In physical world, a PCIe switch including one upstream port and several downstream ports is a single physical device, however we treat each port as a device in qemu world. In qemu docs/pcie.txt, we have below statements: Line 230: Be aware that PCI Express Downstream Ports can't be hot-plugged into Line 231: an existing PCI Express Upstream Port. To my understanding, it implies PCIe downstream ports *can* be hot-plugged into something which is not an existing upstream port. If it is true, how can we do that? AFAIK monitor command device_add can only add one device at a time. Please help to show the truth. Thanks, Heyi