On Wed, 09/12 13:11, Paolo Bonzini wrote: > On 12/09/2018 03:31, Fam Zheng wrote: > >>> > >>> ctx is qemu_aio_context here, so there's no interaction with IOThread. > >> In this case, it should be okay to have the reentrancy, what is the bug > >> that this patch is fixing? > > The same symptom as in the previous patch: virtio_scsi_handle_cmd_vq hangs. > > The > > reason it hangs is fixed by the previous patch, but I don't think it should > > be > > invoked as we're in the middle of virtio_scsi_dataplane_stop(). Applying > > either > > one of the two patches avoids the problem, but this one is more superficial. > > What do you think? > > 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 Fam
