From patchwork Fri Mar 29 09:38:25 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Cindy Lu X-Patchwork-Id: 13610497 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 DB288134BC for ; Fri, 29 Mar 2024 09:38:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711705130; cv=none; b=TUhyqPpsO719SQYHW47w+r53UvakxXZQYOdFXKi3OPSUIGOjFzG55IedttE2Zurm1fdI0JwKxzfNZULjHGxJV5cfJNFPKNWl626jIQilgGawU+8TETVx5Q1wFnFYiiR5u3WKk9sNTxhRn+pw0LCyCnVz2zevM8trWkjwv+KBEiY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711705130; c=relaxed/simple; bh=hlgRWAsqEYqPaeCmYoojJySYxpwBfhEhiWetVJsND38=; h=From:To:Subject:Date:Message-ID:MIME-Version; b=RgVNkkQo071n7oFL6uyLjGlZXwaHf4QN7L/KjjNBMH0LG9ZtkMIRru1vCO9py0sjtnSRzg7D4HmSSXJM1cC9cuqihIMGF3SShOtPRpHTnGYBsRLbHJZ0j2AqU4+dEzm2FlQtK4a0C1bf3rbSbbZFjsXsZ7CuRGjsLjI+/OB38fU= 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=fAxyWxyC; arc=none smtp.client-ip=170.10.129.124 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="fAxyWxyC" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711705127; 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; bh=9TfOEZSUpizBDk/7ZlbtcyuX+Zuz/XZGsV/0/N9TVsY=; b=fAxyWxyCoCHiXru8U8/3tusovyDs2w9GJkOHecM5q5Uc75O/D5NV0mCRCBTbBPHGHjeF2N sdrKm4qZdpwb55v2RLGkSkVAsKAx1/nHgTKmBS5NlSv8I1xx++zVFs8PNEgodDTgFAsDyK f42PaV0AuXpl9eeeXMHLqM9Z/BKKxSI= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-455-jz36XEyxNSOsNelDtdEUBA-1; Fri, 29 Mar 2024 05:38:45 -0400 X-MC-Unique: jz36XEyxNSOsNelDtdEUBA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (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 718DD811E81; Fri, 29 Mar 2024 09:38:45 +0000 (UTC) Received: from server.redhat.com (unknown [10.72.112.204]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6484D202451F; Fri, 29 Mar 2024 09:38:42 +0000 (UTC) From: Cindy Lu To: lulu@redhat.com, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH v2] Documentation: Add reconnect process for VDUSE Date: Fri, 29 Mar 2024 17:38:25 +0800 Message-ID: <20240329093832.140690-1-lulu@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 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/userspace-api/vduse.rst index bdb880e01132..f903aed714d1 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. For more details on the uAPI, please see include/uapi/linux/vduse.h. + +HOW VDUSE devices reconnectoin 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 again + +2. How can I support reconnection in a userspace application? + +2.1 During initialization, the userspace application should first verify the + existence of the device "/dev/vduse/vduse_name". + If it doesn't exist, it means this is the first-time for connection. goto 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_mumber. + +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_FEATURES...) + to get the information from kernel. + Please review the information and confirm if it is suitable to reconnect. + +2.4 Userspace application needs to mmap the memory to userspace + The userspace application requires mapping one page for every vq. These pages + should be used to save vq-related information during system running. Additionally, + 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 information + about reconnections in mapped pages. When calling the ioctl VDUSE_VQ_GET_INFO to + get vq information, it's necessary to check whether it's a reconnection. 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