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=-18.8 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,URIBL_BLOCKED,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 7B0FFC433E6 for ; Fri, 25 Dec 2020 07:00:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 427722313F for ; Fri, 25 Dec 2020 07:00:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726234AbgLYG7r (ORCPT ); Fri, 25 Dec 2020 01:59:47 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56223 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725814AbgLYG7r (ORCPT ); Fri, 25 Dec 2020 01:59:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608879500; 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=IBTp23RhCF2lNaGdXuKBZ6xR632uHIkymwYyPE70oOU=; b=IA4Ua3naXxbrY0tsVTYFCP6FFneeXf/h3cXU+blBsXYa92FYnx7uJ2ofzOdR3hETDDQ6jp EqXjFjyk3XKiUN2zTTiaeemYftRywUiuyrG6YGuMyI3krSHetVdauJq09HrWFe+sfi8Cs8 cuy3W5pcYNoO78T15bAPtInaX7kPkxU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-573-jwRdfOAsMsGt45YAWXmUug-1; Fri, 25 Dec 2020 01:58:16 -0500 X-MC-Unique: jwRdfOAsMsGt45YAWXmUug-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9E8DC10054FF; Fri, 25 Dec 2020 06:58:13 +0000 (UTC) Received: from [10.72.12.97] (ovpn-12-97.pek2.redhat.com [10.72.12.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3962B62462; Fri, 25 Dec 2020 06:58:00 +0000 (UTC) Subject: Re: [RFC v2 09/13] vduse: Add support for processing vhost iotlb message To: Yongji Xie Cc: "Michael S. Tsirkin" , Stefan Hajnoczi , sgarzare@redhat.com, Parav Pandit , akpm@linux-foundation.org, Randy Dunlap , Matthew Wilcox , viro@zeniv.linux.org.uk, axboe@kernel.dk, bcrl@kvack.org, corbet@lwn.net, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org References: <20201222145221.711-1-xieyongji@bytedance.com> <20201222145221.711-10-xieyongji@bytedance.com> <6818a214-d587-4f0b-7de6-13c4e7e94ab6@redhat.com> <595fe7d6-7876-26e4-0b7c-1d63ca6d7a97@redhat.com> From: Jason Wang Message-ID: <0e6faf9c-117a-e23c-8d6d-488d0ec37412@redhat.com> Date: Fri, 25 Dec 2020 14:57:59 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2020/12/24 下午3:37, Yongji Xie wrote: > On Thu, Dec 24, 2020 at 10:41 AM Jason Wang wrote: >> >> On 2020/12/23 下午8:14, Yongji Xie wrote: >>> On Wed, Dec 23, 2020 at 5:05 PM Jason Wang wrote: >>>> On 2020/12/22 下午10:52, Xie Yongji wrote: >>>>> To support vhost-vdpa bus driver, we need a way to share the >>>>> vhost-vdpa backend process's memory with the userspace VDUSE process. >>>>> >>>>> This patch tries to make use of the vhost iotlb message to achieve >>>>> that. We will get the shm file from the iotlb message and pass it >>>>> to the userspace VDUSE process. >>>>> >>>>> Signed-off-by: Xie Yongji >>>>> --- >>>>> Documentation/driver-api/vduse.rst | 15 +++- >>>>> drivers/vdpa/vdpa_user/vduse_dev.c | 147 ++++++++++++++++++++++++++++++++++++- >>>>> include/uapi/linux/vduse.h | 11 +++ >>>>> 3 files changed, 171 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/Documentation/driver-api/vduse.rst b/Documentation/driver-api/vduse.rst >>>>> index 623f7b040ccf..48e4b1ba353f 100644 >>>>> --- a/Documentation/driver-api/vduse.rst >>>>> +++ b/Documentation/driver-api/vduse.rst >>>>> @@ -46,13 +46,26 @@ The following types of messages are provided by the VDUSE framework now: >>>>> >>>>> - VDUSE_GET_CONFIG: Read from device specific configuration space >>>>> >>>>> +- VDUSE_UPDATE_IOTLB: Update the memory mapping in device IOTLB >>>>> + >>>>> +- VDUSE_INVALIDATE_IOTLB: Invalidate the memory mapping in device IOTLB >>>>> + >>>>> Please see include/linux/vdpa.h for details. >>>>> >>>>> -In the data path, VDUSE framework implements a MMU-based on-chip IOMMU >>>>> +The data path of userspace vDPA device is implemented in different ways >>>>> +depending on the vdpa bus to which it is attached. >>>>> + >>>>> +In virtio-vdpa case, VDUSE framework implements a MMU-based on-chip IOMMU >>>>> driver which supports mapping the kernel dma buffer to a userspace iova >>>>> region dynamically. The userspace iova region can be created by passing >>>>> the userspace vDPA device fd to mmap(2). >>>>> >>>>> +In vhost-vdpa case, the dma buffer is reside in a userspace memory region >>>>> +which will be shared to the VDUSE userspace processs via the file >>>>> +descriptor in VDUSE_UPDATE_IOTLB message. And the corresponding address >>>>> +mapping (IOVA of dma buffer <-> VA of the memory region) is also included >>>>> +in this message. >>>>> + >>>>> Besides, the eventfd mechanism is used to trigger interrupt callbacks and >>>>> receive virtqueue kicks in userspace. The following ioctls on the userspace >>>>> vDPA device fd are provided to support that: >>>>> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c >>>>> index b974333ed4e9..d24aaacb6008 100644 >>>>> --- a/drivers/vdpa/vdpa_user/vduse_dev.c >>>>> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c >>>>> @@ -34,6 +34,7 @@ >>>>> >>>>> struct vduse_dev_msg { >>>>> struct vduse_dev_request req; >>>>> + struct file *iotlb_file; >>>>> struct vduse_dev_response resp; >>>>> struct list_head list; >>>>> wait_queue_head_t waitq; >>>>> @@ -325,12 +326,80 @@ static int vduse_dev_set_vq_state(struct vduse_dev *dev, >>>>> return ret; >>>>> } >>>>> >>>>> +static int vduse_dev_update_iotlb(struct vduse_dev *dev, struct file *file, >>>>> + u64 offset, u64 iova, u64 size, u8 perm) >>>>> +{ >>>>> + struct vduse_dev_msg *msg; >>>>> + int ret; >>>>> + >>>>> + if (!size) >>>>> + return -EINVAL; >>>>> + >>>>> + msg = vduse_dev_new_msg(dev, VDUSE_UPDATE_IOTLB); >>>>> + msg->req.size = sizeof(struct vduse_iotlb); >>>>> + msg->req.iotlb.offset = offset; >>>>> + msg->req.iotlb.iova = iova; >>>>> + msg->req.iotlb.size = size; >>>>> + msg->req.iotlb.perm = perm; >>>>> + msg->req.iotlb.fd = -1; >>>>> + msg->iotlb_file = get_file(file); >>>>> + >>>>> + ret = vduse_dev_msg_sync(dev, msg); >>>> My feeling is that we should provide consistent API for the userspace >>>> device to use. >>>> >>>> E.g we'd better carry the IOTLB message for both virtio/vhost drivers. >>>> >>>> It looks to me for virtio drivers we can still use UPDAT_IOTLB message >>>> by using VDUSE file as msg->iotlb_file here. >>>> >>> It's OK for me. One problem is when to transfer the UPDATE_IOTLB >>> message in virtio cases. >> >> Instead of generating IOTLB messages for userspace. >> >> How about record the mappings (which is a common case for device have >> on-chip IOMMU e.g mlx5e and vdpa simlator), then we can introduce ioctl >> for userspace to query? >> > If so, the IOTLB UPDATE is actually triggered by ioctl, but > IOTLB_INVALIDATE is triggered by the message. Is it a little odd? Good point. Some questions here: 1) Userspace think the IOTLB was flushed after IOTLB_INVALIDATE syscall is returned. But this patch doesn't have this guarantee. Can this lead some issues? 2) I think after VDUSE userspace receives IOTLB_INVALIDATE, it needs to issue a munmap(). What if it doesn't do that? > Or > how about trigger it when userspace call mmap() on the device fd? One possible issue is that the IOTLB_UPDATE/INVALIDATE might come after mmap(): 1) When vIOMMU is enabled 2) Guest memory topology has been changed (memory hotplug). Thanks > > Thanks, > Yongji >