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=-9.8 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=ham 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 ECE0CC433E0 for ; Tue, 22 Dec 2020 12:31:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACFEA2312E for ; Tue, 22 Dec 2020 12:31:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726710AbgLVMbE (ORCPT ); Tue, 22 Dec 2020 07:31:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:20990 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726396AbgLVMbD (ORCPT ); Tue, 22 Dec 2020 07:31:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608640176; 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=QvPHQ8PtpFiatjHXDcnf/N48TY86yEtQF2kSghWz0cg=; b=Yhvy56fQkGy7OwEtW95r+TvW5ZSoCMWrH0Kp1snfEpdIOdhMo5QSYwFFThxX54zc+HMWo1 fqdO4/jndBK+LEfWJqX1hqdjyDMVmSBzYdzIro5drbEa5Xf5fmCBiCYFJPoe0w1Vn95wg4 5edM7ueWZZQfjbF5iqEz/Vj0mrMY1Z4= 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-90-TYnFGRoWOBKqln82OvSxaA-1; Tue, 22 Dec 2020 07:29:34 -0500 X-MC-Unique: TYnFGRoWOBKqln82OvSxaA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8F39951081; Tue, 22 Dec 2020 12:29:33 +0000 (UTC) Received: from [10.72.13.168] (ovpn-13-168.pek2.redhat.com [10.72.13.168]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4BE925B4CE; Tue, 22 Dec 2020 12:29:22 +0000 (UTC) Subject: Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device To: Stefano Garzarella Cc: virtualization@lists.linux-foundation.org, Stefan Hajnoczi , Laurent Vivier , linux-kernel@vger.kernel.org, Eli Cohen , "Michael S. Tsirkin" , Max Gurtovoy References: <20201113134712.69744-1-sgarzare@redhat.com> <93f207c0-61e6-3696-f218-e7d7ea9a7c93@redhat.com> <20201218113816.zcyeyqipux4ao4cp@steredhat> <7dd3ed02-36c3-fcfd-0a1d-9c31af6f473e@redhat.com> <20201221111423.sestfroiw2dgpluc@steredhat> <856d53c2-82e2-e408-76e6-24c92010f973@redhat.com> <20201222105733.4f6oou7lshi35qvc@steredhat> From: Jason Wang Message-ID: Date: Tue, 22 Dec 2020 20:29:20 +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: <20201222105733.4f6oou7lshi35qvc@steredhat> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/22 下午6:57, Stefano Garzarella wrote: > On Tue, Dec 22, 2020 at 10:44:48AM +0800, Jason Wang wrote: >> >> On 2020/12/21 下午7:14, Stefano Garzarella wrote: >>> On Mon, Dec 21, 2020 at 11:16:54AM +0800, Jason Wang wrote: >>>> >>>> On 2020/12/18 下午7:38, Stefano Garzarella wrote: >>>>> On Mon, Nov 16, 2020 at 11:37:48AM +0800, Jason Wang wrote: >>>>>> >>>>>> On 2020/11/13 下午9:47, Stefano Garzarella wrote: >>>>>>> Thanks to Max that started this work! >>>>>>> I took his patches, and extended the block simulator a bit. >>>>>>> >>>>>>> This series moves the network device simulator in a new module >>>>>>> (vdpa_sim_net) and leaves the generic functions in the vdpa_sim >>>>>>> core >>>>>>> module, allowing the possibility to add new vDPA device simulators. >>>>>>> Then we added a new vdpa_sim_blk module to simulate a block device. >>>>>>> >>>>>>> I'm not sure about patch 11 ("vringh: allow vringh_iov_xfer() to >>>>>>> skip >>>>>>> bytes when ptr is NULL"), maybe we can add a new functions >>>>>>> instead of >>>>>>> modify vringh_iov_xfer(). >>>>>>> >>>>>>> As Max reported, I'm also seeing errors with vdpa_sim_blk >>>>>>> related to >>>>>>> iotlb and vringh when there is high load, these are some of the >>>>>>> error >>>>>>> messages I can see randomly: >>>>>>> >>>>>>>   vringh: Failed to access avail idx at 00000000e8deb2cc >>>>>>>   vringh: Failed to read head: idx 6289 address 00000000e1ad1d50 >>>>>>>   vringh: Failed to get flags at 000000006635d7a3 >>>>>>> >>>>>>>   virtio_vdpa vdpa0: vringh_iov_push_iotlb() error: -14 offset: >>>>>>>   0x2840000 len: 0x20000 >>>>>>>   virtio_vdpa vdpa0: vringh_iov_pull_iotlb() error: -14 offset: >>>>>>>   0x58ee000 len: 0x3000 >>>>>>> >>>>>>> These errors should all be related to the fact that >>>>>>> iotlb_translate() >>>>>>> fails with -EINVAL, so it seems that we miss some mapping. >>>>>> >>>>>> >>>>>> Is this only reproducible when there's multiple co-current >>>>>> accessing of IOTLB? If yes, it's probably a hint that some kind >>>>>> of synchronization is still missed somewhere. >>>>>> >>>>>> It might be useful to log the dma_map/unmp in both virtio_ring >>>>>> and vringh to see who is missing the map. >>>>>> >>>>> >>>>> Just an update about these issues with vdpa-sim-blk. >>>>> I've been focusing a little bit on these failures over the last >>>>> few days and have found two issues related to the IOTLB/IOMMU: >>>>> >>>>> 1. Some requests coming from the block layer fills the SG list >>>>> with multiple buffers that had the same physical address. This >>>>> happens for example while using 'mkfs', at some points multiple >>>>> sectors are zeroed so multiple SG elements point to the same >>>>> physical page that is zeroed. >>>>> Since we are using vhost_iotlb_del_range() in the >>>>> vdpasim_unmap_page(), this removes all the overlapped ranges. I >>>>> fixed removing a single map in vdpasim_unmap_page(), but has an >>>>> alternative we can implement some kind of reference counts. >>>> >>>> >>>> I think we need to do what hardware do. So using refcount is >>>> probably not a good ida. >>> >>> Okay, so since we are using for simplicity an identical mapping, we >>> are assigning the same dma_addr to multiple pages. >> >> >> I think I get you now. That's the root cause for the failure. > > Yes, sorry, I didn't explain well previously. > >> >> Then I think we need an simple iova allocator for vdpa simulator, and >> it might be useful for VDUSE as well. > > Okay, I'll work on it. > If you have an example to follow or some pointers, they are welcome :-) Kernel had implemented one in iova.c but I'm not sure we need the complexity like that. Or we can just use rbtree or idr to implement a simpler one. Thanks > > Thanks, > Stefano >