Messages in this thread | | | Subject | Re: [PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device | From | Jason Wang <> | Date | Tue, 22 Dec 2020 20:29:20 +0800 |
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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.
Thanks
> > Thanks, > Stefano >
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