From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15403C432BE for ; Mon, 23 Aug 2021 07:55:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC33E61374 for ; Mon, 23 Aug 2021 07:55:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235467AbhHWHzt (ORCPT ); Mon, 23 Aug 2021 03:55:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:45519 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235100AbhHWHzs (ORCPT ); Mon, 23 Aug 2021 03:55:48 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629705305; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=/hocWjKMUK0ZY0xyvvkq28cKqCTWsZd73eIRRl/mYVE=; b=LlK1RehEPKbAdKV69JsF/1p0w66+lhh/L4EN61zg8evrCA8DfJ+mIBjyrQwjV+YjQoMZFw koYfMird82+espVFvNt76rDzaudn4MuSV1/n4/PI83dpq3Vs8qW0p9kVFivkrW7pNGNGJV 9t85/GbylYRWYVyyr9n7LpYOoAyHGto= Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-28-fTS0XZuEOFKUNs5oNmDPfQ-1; Mon, 23 Aug 2021 03:55:04 -0400 X-MC-Unique: fTS0XZuEOFKUNs5oNmDPfQ-1 Received: by mail-pj1-f72.google.com with SMTP id k23-20020a17090a591700b001796382f0d7so10932487pji.5 for ; Mon, 23 Aug 2021 00:55:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=/hocWjKMUK0ZY0xyvvkq28cKqCTWsZd73eIRRl/mYVE=; b=H/tbPcCo/1mt6AAIBNivfVrqglERzxMec3LVMTuNd5ArX7zi0ISbUVm7LQSasturly VE/Q1NprS03NOM8H4q34uuNGA1H2Qp5IVvIsTIC8Mavgbi3T6Qajv1tQ9WcIXY7rHumg 0frRJlVPDRJtGorhyAYjCEEKpKeVXFUTevo1zCJ0xZ6QivNJSDbRPPWTsEQtqS6rVywN WzNAnAKrG0ruVvpMTbGTT7lstWzzwB/fPkb2f2G3lGDZbqrVjqJiWwWrMxqa8k/tSm7q pWIo8fv+FEGaEIAFxAz41t0zLTmAeS5gA2iYYAdpd/sRSr95SbVD5hWgl95qs1mYhC1Q oyVQ== X-Gm-Message-State: AOAM53351nAkB0UtjJU6Wsgf2RjUUfYn8NmKj95AnILUtGzG5uEB+ZK/ F5hu5EcTULK6h/c3nqnlPYGpezF0cGipR7HQHDOFZVn5aIP63jsq09zKYTIwpy+IgKu4PAXgE0t t2ddTF8jhHoxt X-Received: by 2002:a63:5b01:: with SMTP id p1mr30762349pgb.250.1629705303563; Mon, 23 Aug 2021 00:55:03 -0700 (PDT) X-Google-Smtp-Source: ABdhPJy/gdooVRaBJkpdnxcchxAVLcay4ARXGkH6bG99GZDLGfQfCwwVMA6TovyMi4F/iOGpo+25iw== X-Received: by 2002:a63:5b01:: with SMTP id p1mr30762322pgb.250.1629705303264; Mon, 23 Aug 2021 00:55:03 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id fh2sm13229446pjb.12.2021.08.23.00.54.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Aug 2021 00:55:02 -0700 (PDT) Subject: Re: [PATCH v11 12/12] Documentation: Add documentation for VDUSE To: Xie Yongji , mst@redhat.com, stefanha@redhat.com, sgarzare@redhat.com, parav@nvidia.com, hch@infradead.org, christian.brauner@canonical.com, rdunlap@infradead.org, willy@infradead.org, viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org, corbet@lwn.net, mika.penttila@nextfour.com, dan.carpenter@oracle.com, joro@8bytes.org, gregkh@linuxfoundation.org, zhe.he@windriver.com, xiaodong.liu@intel.com, joe@perches.com, robin.murphy@arm.com Cc: songmuchun@bytedance.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <20210818120642.165-1-xieyongji@bytedance.com> <20210818120642.165-13-xieyongji@bytedance.com> From: Jason Wang Message-ID: Date: Mon, 23 Aug 2021 15:54:50 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210818120642.165-13-xieyongji@bytedance.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org ÔÚ 2021/8/18 ÏÂÎç8:06, Xie Yongji дµÀ: > VDUSE (vDPA Device in Userspace) is a framework to support > implementing software-emulated vDPA devices in userspace. This > document is intended to clarify the VDUSE design and usage. > > Signed-off-by: Xie Yongji Acked-by: Jason Wang > --- > Documentation/userspace-api/index.rst | 1 + > Documentation/userspace-api/vduse.rst | 233 ++++++++++++++++++++++++++++++++++ > 2 files changed, 234 insertions(+) > create mode 100644 Documentation/userspace-api/vduse.rst > > diff --git a/Documentation/userspace-api/index.rst b/Documentation/userspace-api/index.rst > index 0b5eefed027e..c432be070f67 100644 > --- a/Documentation/userspace-api/index.rst > +++ b/Documentation/userspace-api/index.rst > @@ -27,6 +27,7 @@ place where this information is gathered. > iommu > media/index > sysfs-platform_profile > + vduse > > .. only:: subproject and html > > diff --git a/Documentation/userspace-api/vduse.rst b/Documentation/userspace-api/vduse.rst > new file mode 100644 > index 000000000000..42ef59ea5314 > --- /dev/null > +++ b/Documentation/userspace-api/vduse.rst > @@ -0,0 +1,233 @@ > +================================== > +VDUSE - "vDPA Device in Userspace" > +================================== > + > +vDPA (virtio data path acceleration) device is a device that uses a > +datapath which complies with the virtio specifications with vendor > +specific control path. vDPA devices can be both physically located on > +the hardware or emulated by software. VDUSE is a framework that makes it > +possible to implement software-emulated vDPA devices in userspace. And > +to make the device emulation more secure, the emulated vDPA device's > +control path is handled in the kernel and only the data path is > +implemented in the userspace. > + > +Note that only virtio block device is supported by VDUSE framework now, > +which can reduce security risks when the userspace process that implements > +the data path is run by an unprivileged user. The support for other device > +types can be added after the security issue of corresponding device driver > +is clarified or fixed in the future. > + > +Create/Destroy VDUSE devices > +------------------------ > + > +VDUSE devices are created as follows: > + > +1. Create a new VDUSE instance with ioctl(VDUSE_CREATE_DEV) on > + /dev/vduse/control. > + > +2. Setup each virtqueue with ioctl(VDUSE_VQ_SETUP) on /dev/vduse/$NAME. > + > +3. Begin processing VDUSE messages from /dev/vduse/$NAME. The first > + messages will arrive while attaching the VDUSE instance to vDPA bus. > + > +4. Send the VDPA_CMD_DEV_NEW netlink message to attach the VDUSE > + instance to vDPA bus. > + > +VDUSE devices are destroyed as follows: > + > +1. Send the VDPA_CMD_DEV_DEL netlink message to detach the VDUSE > + instance from vDPA bus. > + > +2. Close the file descriptor referring to /dev/vduse/$NAME. > + > +3. Destroy the VDUSE instance with ioctl(VDUSE_DESTROY_DEV) on > + /dev/vduse/control. > + > +The netlink messages can be sent via vdpa tool in iproute2 or use the > +below sample codes: > + > +.. code-block:: c > + > + static int netlink_add_vduse(const char *name, enum vdpa_command cmd) > + { > + struct nl_sock *nlsock; > + struct nl_msg *msg; > + int famid; > + > + nlsock = nl_socket_alloc(); > + if (!nlsock) > + return -ENOMEM; > + > + if (genl_connect(nlsock)) > + goto free_sock; > + > + famid = genl_ctrl_resolve(nlsock, VDPA_GENL_NAME); > + if (famid < 0) > + goto close_sock; > + > + msg = nlmsg_alloc(); > + if (!msg) > + goto close_sock; > + > + if (!genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, famid, 0, 0, cmd, 0)) > + goto nla_put_failure; > + > + NLA_PUT_STRING(msg, VDPA_ATTR_DEV_NAME, name); > + if (cmd == VDPA_CMD_DEV_NEW) > + NLA_PUT_STRING(msg, VDPA_ATTR_MGMTDEV_DEV_NAME, "vduse"); > + > + if (nl_send_sync(nlsock, msg)) > + goto close_sock; > + > + nl_close(nlsock); > + nl_socket_free(nlsock); > + > + return 0; > + nla_put_failure: > + nlmsg_free(msg); > + close_sock: > + nl_close(nlsock); > + free_sock: > + nl_socket_free(nlsock); > + return -1; > + } > + > +How VDUSE works > +--------------- > + > +As mentioned above, a VDUSE device is created by ioctl(VDUSE_CREATE_DEV) on > +/dev/vduse/control. With this ioctl, userspace can specify some basic configuration > +such as device name (uniquely identify a VDUSE device), virtio features, virtio > +configuration space, the number of virtqueues and so on for this emulated device. > +Then a char device interface (/dev/vduse/$NAME) is exported to userspace for device > +emulation. Userspace can use the VDUSE_VQ_SETUP ioctl on /dev/vduse/$NAME to > +add per-virtqueue configuration such as the max size of virtqueue to the device. > + > +After the initialization, the VDUSE device can be attached to vDPA bus via > +the VDPA_CMD_DEV_NEW netlink message. Userspace needs to read()/write() on > +/dev/vduse/$NAME to receive/reply some control messages from/to VDUSE kernel > +module as follows: > + > +.. code-block:: c > + > + static int vduse_message_handler(int dev_fd) > + { > + int len; > + struct vduse_dev_request req; > + struct vduse_dev_response resp; > + > + len = read(dev_fd, &req, sizeof(req)); > + if (len != sizeof(req)) > + return -1; > + > + resp.request_id = req.request_id; > + > + switch (req.type) { > + > + /* handle different types of messages */ > + > + } > + > + len = write(dev_fd, &resp, sizeof(resp)); > + if (len != sizeof(resp)) > + return -1; > + > + return 0; > + } > + > +There are now three types of messages introduced by VDUSE framework: > + > +- VDUSE_GET_VQ_STATE: Get the state for virtqueue, userspace should return > + avail index for split virtqueue or the device/driver ring wrap counters and > + the avail and used index for packed virtqueue. > + > +- VDUSE_SET_STATUS: Set the device status, userspace should follow > + the virtio spec: https://docs.oasis-open.org/virtio/virtio/v1.1/virtio-v1.1.html > + to process this message. For example, fail to set the FEATURES_OK device > + status bit if the device can not accept the negotiated virtio features > + get from the VDUSE_DEV_GET_FEATURES ioctl. > + > +- VDUSE_UPDATE_IOTLB: Notify userspace to update the memory mapping for specified > + IOVA range, userspace should firstly remove the old mapping, then setup the new > + mapping via the VDUSE_IOTLB_GET_FD ioctl. > + > +After DRIVER_OK status bit is set via the VDUSE_SET_STATUS message, userspace is > +able to start the dataplane processing as follows: > + > +1. Get the specified virtqueue's information with the VDUSE_VQ_GET_INFO ioctl, > + including the size, the IOVAs of descriptor table, available ring and used ring, > + the state and the ready status. > + > +2. Pass the above IOVAs to the VDUSE_IOTLB_GET_FD ioctl so that those IOVA regions > + can be mapped into userspace. Some sample codes is shown below: > + > +.. code-block:: c > + > + static int perm_to_prot(uint8_t perm) > + { > + int prot = 0; > + > + switch (perm) { > + case VDUSE_ACCESS_WO: > + prot |= PROT_WRITE; > + break; > + case VDUSE_ACCESS_RO: > + prot |= PROT_READ; > + break; > + case VDUSE_ACCESS_RW: > + prot |= PROT_READ | PROT_WRITE; > + break; > + } > + > + return prot; > + } > + > + static void *iova_to_va(int dev_fd, uint64_t iova, uint64_t *len) > + { > + int fd; > + void *addr; > + size_t size; > + struct vduse_iotlb_entry entry; > + > + entry.start = iova; > + entry.last = iova; > + > + /* > + * Find the first IOVA region that overlaps with the specified > + * range [start, last] and return the corresponding file descriptor. > + */ > + fd = ioctl(dev_fd, VDUSE_IOTLB_GET_FD, &entry); > + if (fd < 0) > + return NULL; > + > + size = entry.last - entry.start + 1; > + *len = entry.last - iova + 1; > + addr = mmap(0, size, perm_to_prot(entry.perm), MAP_SHARED, > + fd, entry.offset); > + close(fd); > + if (addr == MAP_FAILED) > + return NULL; > + > + /* > + * Using some data structures such as linked list to store > + * the iotlb mapping. The munmap(2) should be called for the > + * cached mapping when the corresponding VDUSE_UPDATE_IOTLB > + * message is received or the device is reset. > + */ > + > + return addr + iova - entry.start; > + } > + > +3. Setup the kick eventfd for the specified virtqueues with the VDUSE_VQ_SETUP_KICKFD > + ioctl. The kick eventfd is used by VDUSE kernel module to notify userspace to > + consume the available ring. This is optional since userspace can choose to poll the > + available ring instead. > + > +4. Listen to the kick eventfd (optional) and consume the available ring. The buffer > + described by the descriptors in the descriptor table should be also mapped into > + userspace via the VDUSE_IOTLB_GET_FD ioctl before accessing. > + > +5. Inject an interrupt for specific virtqueue with the VDUSE_INJECT_VQ_IRQ ioctl > + after the used ring is filled. > + > +For more details on the uAPI, please see include/uapi/linux/vduse.h.