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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id c10sm27792009wrb.92.2020.12.21.03.14.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 21 Dec 2020 03:14:25 -0800 (PST) Date: Mon, 21 Dec 2020 12:14:23 +0100 From: Stefano Garzarella To: Jason Wang Cc: virtualization@lists.linux-foundation.org, Stefan Hajnoczi , Laurent Vivier , linux-kernel@vger.kernel.org, Eli Cohen , "Michael S. Tsirkin" , Max Gurtovoy Subject: Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device Message-ID: <20201221111423.sestfroiw2dgpluc@steredhat> References: <20201113134712.69744-1-sgarzare@redhat.com> <93f207c0-61e6-3696-f218-e7d7ea9a7c93@redhat.com> <20201218113816.zcyeyqipux4ao4cp@steredhat> <7dd3ed02-36c3-fcfd-0a1d-9c31af6f473e@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7dd3ed02-36c3-fcfd-0a1d-9c31af6f473e@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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 >> >