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=-7.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 0F868C43461 for ; Mon, 12 Apr 2021 09:45:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E292161249 for ; Mon, 12 Apr 2021 09:45:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240608AbhDLJpi (ORCPT ); Mon, 12 Apr 2021 05:45:38 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:27247 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238998AbhDLJiF (ORCPT ); Mon, 12 Apr 2021 05:38:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618220266; 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=Wmf9ZGvB5vcgO4CtC2CcyvvFrlcqG76wOFO2zMFyTks=; b=SJtq2YvQJBoc5KWJAMebr/Tz4VxDLtsj8d19shAYA2ctnSU3PfKL6lnk/MKFkgTkwwu0XI JjeaddZfyf7pGM7yR8aXDY3OVfpznP7VNAdQk+fOK6VB7kF17R/O9HKMxaTN/3qY1rctvM RjZfiFUd9kLdDEdwkC4YX4/Eb/I00lo= 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-309-78krYvl8MyOKYKMjDvetRQ-1; Mon, 12 Apr 2021 05:37:44 -0400 X-MC-Unique: 78krYvl8MyOKYKMjDvetRQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4287083DD20; Mon, 12 Apr 2021 09:37:42 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-232.pek2.redhat.com [10.72.13.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 687B25D9DE; Mon, 12 Apr 2021 09:37:28 +0000 (UTC) Subject: Re: [PATCH v6 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace To: Yongji Xie Cc: "Michael S. Tsirkin" , Stefan Hajnoczi , Stefano Garzarella , Parav Pandit , Christoph Hellwig , Christian Brauner , Randy Dunlap , Matthew Wilcox , viro@zeniv.linux.org.uk, Jens Axboe , bcrl@kvack.org, Jonathan Corbet , =?UTF-8?Q?Mika_Penttil=c3=a4?= , Dan Carpenter , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20210331080519.172-1-xieyongji@bytedance.com> <20210331080519.172-10-xieyongji@bytedance.com> <091dde74-449b-385c-0ec9-11e4847c6c4c@redhat.com> From: Jason Wang Message-ID: <0f386dfe-45c9-5609-55f7-b8ab2a4abf5e@redhat.com> Date: Mon, 12 Apr 2021 17:37:26 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 在 2021/4/12 下午4:02, Yongji Xie 写道: > On Mon, Apr 12, 2021 at 3:16 PM Jason Wang wrote: >> >> 在 2021/4/9 下午4:02, Yongji Xie 写道: >>>>>>> +}; >>>>>>> + >>>>>>> +struct vduse_dev_config_data { >>>>>>> + __u32 offset; /* offset from the beginning of config space */ >>>>>>> + __u32 len; /* the length to read/write */ >>>>>>> + __u8 data[VDUSE_CONFIG_DATA_LEN]; /* data buffer used to read/write */ >>>>>> Note that since VDUSE_CONFIG_DATA_LEN is part of uAPI it means we can >>>>>> not change it in the future. >>>>>> >>>>>> So this might suffcient for future features or all type of virtio devices. >>>>>> >>>>> Do you mean 256 is no enough here？ >>>> Yes. >>>> >>> But this request will be submitted multiple times if config lengh is >>> larger than 256. So do you think whether we need to extent the size to >>> 512 or larger? >> >> So I think you'd better either: >> >> 1) document the limitation (256) in somewhere, (better both uapi and doc) >> > But the VDUSE_CONFIG_DATA_LEN doesn't mean the limitation of > configuration space. It only means the maximum size of one data > transfer for configuration space. Do you mean document this? Yes, and another thing is that since you're using data[VDUSE_CONFIG_DATA_LEN] in the uapi, it implies the length is always 256 which seems not good and not what the code is wrote. Thanks > > Thanks, > Yongji >