From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37723) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aIqXZ-0007D3-U3 for qemu-devel@nongnu.org; Mon, 11 Jan 2016 23:26:43 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aIqXX-0000Fa-9B for qemu-devel@nongnu.org; Mon, 11 Jan 2016 23:26:41 -0500 Received: from mail-pa0-x230.google.com ([2607:f8b0:400e:c03::230]:33095) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aIqXX-0000FJ-0g for qemu-devel@nongnu.org; Mon, 11 Jan 2016 23:26:39 -0500 Received: by mail-pa0-x230.google.com with SMTP id cy9so332753973pac.0 for ; Mon, 11 Jan 2016 20:26:38 -0800 (PST) References: <1449201120-3432-1-git-send-email-mukawa@igel.co.jp> <87oacrsz1p.fsf@blackfin.pond.sub.org> From: Tetsuya Mukawa Message-ID: <5694807A.3000002@igel.co.jp> Date: Tue, 12 Jan 2016 13:26:34 +0900 MIME-Version: 1.0 In-Reply-To: <87oacrsz1p.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PATCH] ivshmem: Store file descriptor for vhost-user negotiation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= Cc: QEMU , "Michael S. Tsirkin" On 2016/01/12 4:20, Markus Armbruster wrote: > Marc-André Lureau writes: > >> Hi >> >> On Fri, Dec 4, 2015 at 3:55 PM, Tetsuya Mukawa wrote: >>>> What's the use case or test case? >>> One of example is userspace device driver like DPDK PMD. >>> Actually, I've found this fd related behavior using DPDK virtio-net PMD. >>> Could you please check below to know my use case more? >>> http://thread.gmane.org/gmane.comp.networking.dpdk.devel/28467/focus=28493 >> Thanks. Why not use memory-backend-file with share=on ? I think I >> understand you want to use the same BAR address as the host shared >> memory location to avoid extra offset computation. I don't know about >> the limitations here. Is this extra offset really worth saving? >> Finally, I wonder what qemu is really doing in the end ;) > Tetsuya, I still don't understand what you're trying to accomplish. Hi Markus, Please let me describe it more. We have below test program for vhost-user. - ./tests/vhost-user-test.c This program doesn't share memory between test process and QEMU process. So all memory accesses are sent as qtest command. If both process has a shared memory that can be accessed using same address by both processes, we can reduce above memory accessing overhead. This is what I want to do. So far, when vhost-user is used, the memory will not be shared because fd isn't kept. This is what I want to fix. > I concur with Marc-André that -object memory-backend-FOO is how we > allocate a memory object for something else to use. I am not so familiar with QEMU memory architecture. So please let me make sure. Does vhost-user only works with memory backend objects? If it's correct, in my case, I want to use an unix domain socket to transfer fd of the shared memory. To do that, do you suggest me to add 'chardev' parameter to ./backend/hostmem-file.c? Tetsuya > >> Michael, could you comment about this vhost-user use case? (see above >> linked thread)