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=-8.5 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 D5BF0C433DB for ; Tue, 22 Dec 2020 02:46:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9ED3D22B2B for ; Tue, 22 Dec 2020 02:46:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725975AbgLVCqb (ORCPT ); Mon, 21 Dec 2020 21:46:31 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:35572 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725924AbgLVCqa (ORCPT ); Mon, 21 Dec 2020 21:46:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608605103; 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=mtrZTTJIr7oR1Tjy1htJ8dmZVuN7yGZCQoQCqS0N9aA=; b=IOWNDpbMOf4VXM2Z4ZfL3zwHipsPL2xunAy06hjGmv0LrWMO4NshiSqhyx7RbDscbr/9q/ NBuXrlYf6PH+Gdf9udvY0ar68+Ar9xhkYCPh7MDumBR7KbwnlYfNdCz49ydJ+5V1HlQX+Q Sv/oEvJ5HcIynGMcD3OIchOx3CH8KIk= 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-30-SL4XcIw9NsKPmHr7FDGARw-1; Mon, 21 Dec 2020 21:45:00 -0500 X-MC-Unique: SL4XcIw9NsKPmHr7FDGARw-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 A3D26801817; Tue, 22 Dec 2020 02:44:59 +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 3E66F5D6D1; Tue, 22 Dec 2020 02:44:49 +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> From: Jason Wang Message-ID: <856d53c2-82e2-e408-76e6-24c92010f973@redhat.com> Date: Tue, 22 Dec 2020 10:44:48 +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: <20201221111423.sestfroiw2dgpluc@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 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Then I think we need an simple iova allocator for vdpa simulator, and it might be useful for VDUSE as well. Thanks > > So, it should be okay to remove a single mapping checking the others > parameters (i.e. dir, size). > > I'll send a patch, so with the code it should be easier :-) > > Thanks, > Stefano > >> >> >>> >>> 2. There was a race between dma_map/unmap and the worker thread, >>> since both are accessing the IOMMU. Taking the iommu_lock while >>> using vhost_iotlb_* API in the worker thread fixes the "vringh: >>> Failed to *" issues. >>> >>> Whit these issues fixed the vdpa-blk simulator seems to work well. >>> I'll send the patches next week or after the break. >> >> >> Good to know this. >> >> Thanks >> >> >>> >>> Thanks, >>> Stefano >>> >> >