Messages in this thread | | | Subject | Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device | From | Jason Wang <> | Date | Mon, 21 Dec 2020 11:16:54 +0800 |
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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.
> > 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 >
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