From nobody Thu Dec 18 07:20:15 2025 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BF8D8287D for ; Fri, 12 Apr 2024 13:31:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712928692; cv=none; b=BVOWwCUGoZZFtUZ7zyUa6lt8ChvlOokKG8S/Q++wI2oiUN0OpvUzCr68J/Z41JF19bCu11xVy6dHUENn6RRkOcZLEHVntDjGe5NkGVX7OTmElI1aNp5m3xbHYbY+C+fbfTFj7qx3shGtkw/tpfyu1JrvmMoZ1xvDL12LiSv24/A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712928692; c=relaxed/simple; bh=6bmbdoifZb2Jpy0PZiNXlrBy305qSk1zWYVTLBSmB0M=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=a7TuahFj5piljeAuQST3lmtSpCC54ldyqcplq2XJWsztIjCrsgopPM3FIYyZPVenVVKgqHP/gpRydxN7BrCvsVK3HnPjYbEiX6KEdI9rXMWDS0nKeJxxyUU5xTuBhxTG83sEfuuz2G97WWPwhI/xYeWQRFAKnwP33Hcf0O6zA8Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=PN+DHwX3; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="PN+DHwX3" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1712928690; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Vba8fCSuLQZTKX30MTVAeYL8D2lP6F44uKwflbfLdSs=; b=PN+DHwX3v5/GBzSxmN/j6yA9XkwdoV9kDNrT4uxNYuA4+1RcmmWUck3rct1lTdPHXTxyea fOD9JnpfO9rEI5G+2WHgLpg6kU7w0bLuNY+t9EZ3tafXTOsVFGeAB60+U+C6VebPZGV6+u Q4dre0xaK/MeiO9t0MELhZ9X1b/HEx8= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-286-W-X8IWsyOMeVoJYzPPGdhQ-1; Fri, 12 Apr 2024 09:31:29 -0400 X-MC-Unique: W-X8IWsyOMeVoJYzPPGdhQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EEACA28C97D1; Fri, 12 Apr 2024 13:31:28 +0000 (UTC) Received: from server.redhat.com (unknown [10.72.112.22]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9935310E47; Fri, 12 Apr 2024 13:31:26 +0000 (UTC) From: Cindy Lu To: lulu@redhat.com, jasowang@redhat.com, mst@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: [PATCH v5 5/5] Documentation: Add reconnect process for VDUSE Date: Fri, 12 Apr 2024 21:28:25 +0800 Message-ID: <20240412133017.483407-6-lulu@redhat.com> In-Reply-To: <20240412133017.483407-1-lulu@redhat.com> References: <20240412133017.483407-1-lulu@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.5 Content-Type: text/plain; charset="utf-8" Add a document explaining the reconnect process, including what the Userspace App needs to do and how it works with the kernel. Signed-off-by: Cindy Lu --- Documentation/userspace-api/vduse.rst | 41 +++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) diff --git a/Documentation/userspace-api/vduse.rst b/Documentation/userspac= e-api/vduse.rst index bdb880e01132..7faa83462e78 100644 --- a/Documentation/userspace-api/vduse.rst +++ b/Documentation/userspace-api/vduse.rst @@ -231,3 +231,44 @@ able to start the dataplane processing as follows: after the used ring is filled. =20 For more details on the uAPI, please see include/uapi/linux/vduse.h. + +HOW VDUSE devices reconnection works +------------------------------------ +1. What is reconnection? + + When the userspace application loads, it should establish a connection + to the vduse kernel device. Sometimes,the userspace application exists, + and we want to support its restart and connect to the kernel device aga= in + +2. How can I support reconnection in a userspace application? + +2.1 During initialization, the userspace application should first verify t= he + existence of the device "/dev/vduse/vduse_name". + If it doesn't exist, it means this is the first-time for connection. g= oto step 2.2 + If it exists, it means this is a reconnection, and we should goto step= 2.3 + +2.2 Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on + /dev/vduse/control. + When ioctl(VDUSE_CREATE_DEV) is called, kernel allocates memory for + the reconnect information. The total memory size is PAGE_SIZE*vq_mumbe= r. + +2.3 Check if the information is suitable for reconnect + If this is reconnection : + Before attempting to reconnect, The userspace application needs to use= the + ioctl(VDUSE_DEV_GET_CONFIG, VDUSE_DEV_GET_STATUS, VDUSE_DEV_GET_FEATUR= ES...) + to get the information from kernel. + Please review the information and confirm if it is suitable to reconne= ct. + +2.4 Userspace application needs to mmap the memory to userspace + The userspace application requires mapping one page for every vq. Thes= e pages + should be used to save vq-related information during system running. A= dditionally, + the application must define its own structure to store information for= reconnection. + +2.5 Completed the initialization and running the application. + While the application is running, it is important to store relevant in= formation + about reconnections in mapped pages. When calling the ioctl VDUSE_VQ_G= ET_INFO to + get vq information, it's necessary to check whether it's a reconnectio= n. If it is + a reconnection, the vq-related information must be get from the mapped= pages. + +2.6 When the Userspace application exits, it is necessary to unmap all the + pages for reconnection --=20 2.43.0