On Wed, 09/12 14:42, Paolo Bonzini wrote: > On 12/09/2018 13:50, Fam Zheng wrote: > >> I think it's okay if it is invoked. The sequence is first you stop the > >> vq, then you drain the BlockBackends, then you switch AioContext. All > >> that matters is the outcome when virtio_scsi_dataplane_stop returns. > > Yes, but together with vIOMMU, it also effectively leads to a > > virtio_error(), > > which is not clean. QEMU stderr when this call happens (with patch 1 but not > > this patch): > > > > 2018-09-12T11:48:10.193023Z qemu-system-x86_64: vtd_iommu_translate: > > detected translation failure (dev=02:00:00, iova=0x0) > > 2018-09-12T11:48:10.193044Z qemu-system-x86_64: New fault is not recorded > > due to compression of faults > > 2018-09-12T11:48:10.193061Z qemu-system-x86_64: virtio: zero sized buffers > > are not allowed > > But with iothread, virtio_scsi_dataplane_stop runs in another thread > than the iothread; in that case you still have a race where the iothread > can process the vq before aio_disable_external and print the error. > > IIUC the guest has cleared the IOMMU page tables _before_ clearing the > DRIVER_OK bit in the status field. Could this be a guest bug? >
I'm not sure if it is a bug or not. I think what happens is the device is left enabled by Seabios, and then reset by kernel. Fam
