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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id z22sm25892487wml.1.2020.12.22.02.57.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 22 Dec 2020 02:57:36 -0800 (PST) Date: Tue, 22 Dec 2020 11:57:33 +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: <20201222105733.4f6oou7lshi35qvc@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> <20201221111423.sestfroiw2dgpluc@steredhat> <856d53c2-82e2-e408-76e6-24c92010f973@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: <856d53c2-82e2-e408-76e6-24c92010f973@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 :-) Thanks, Stefano