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[23.128.96.18]) by mx.google.com with ESMTP id ga29si2038022ejc.421.2020.12.22.05.00.19; Tue, 22 Dec 2020 05:00:42 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=BpjFRhCD; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726716AbgLVM6G (ORCPT + 99 others); Tue, 22 Dec 2020 07:58:06 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:52629 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725846AbgLVM6G (ORCPT ); Tue, 22 Dec 2020 07:58:06 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608641799; 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=ogZRhqVu5q9mojvGMAotSvNvS5JdueUvVG0eDaDK5jw=; b=BpjFRhCD9tGGEbbGUIUngYCiT3uSDzgWu+szuWZOSLTrx7ClfXoQDbIyLMdE52yMP7lO5e 8Yg7sP31MWpkplQfDYZWlepXVzY/9YZu5XQfESzgvJsLUvigfwxsjN11Q6fzzcU5afQiML hYl1rTCQ1MEk2pE3nsPgtBz55HMIImc= 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-36-J9s2d9tfOFmaagKMummreA-1; Tue, 22 Dec 2020 07:56:35 -0500 X-MC-Unique: J9s2d9tfOFmaagKMummreA-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 10EF61005504; Tue, 22 Dec 2020 12:56:34 +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 28B5039A62; Tue, 22 Dec 2020 12:56:23 +0000 (UTC) Subject: Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device From: Jason Wang 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> Message-ID: <0a3c1304-6ed3-d68d-848c-1c9871f8dd53@redhat.com> Date: Tue, 22 Dec 2020 20:56:16 +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 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/12/22 下午8:29, Jason Wang wrote: > > 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. VDUSE[1] implements another allocator, but it's still complicated since it needs to track bounce pages. I feel like we'd better start from a simple one. Thanks [1] https://www.spinics.net/lists/linux-mm/msg231576.html > > Thanks > > >> >> Thanks, >> Stefano >>