Stefano Garzarella
2020-Dec-22 10:57 UTC
[PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device
On Tue, Dec 22, 2020 at 10:44:48AM +0800, Jason Wang wrote:> >On 2020/12/21 ??7:14, Stefano Garzarella wrote: >>On Mon, Dec 21, 2020 at 11:16:54AM +0800, Jason Wang wrote: >>> >>>On 2020/12/18 ??7:38, Stefano Garzarella wrote: >>>>On Mon, Nov 16, 2020 at 11:37:48AM +0800, Jason Wang wrote: >>>>> >>>>>On 2020/11/13 ??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
Jason Wang
2020-Dec-22 12:29 UTC
[PATCH RFC 00/12] vdpa: generalize vdpa simulator and add block device
On 2020/12/22 ??6:57, Stefano Garzarella wrote:> On Tue, Dec 22, 2020 at 10:44:48AM +0800, Jason Wang wrote: >> >> On 2020/12/21 ??7:14, Stefano Garzarella wrote: >>> On Mon, Dec 21, 2020 at 11:16:54AM +0800, Jason Wang wrote: >>>> >>>> On 2020/12/18 ??7:38, Stefano Garzarella wrote: >>>>> On Mon, Nov 16, 2020 at 11:37:48AM +0800, Jason Wang wrote: >>>>>> >>>>>> On 2020/11/13 ??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 >