Hi, I tested it today and there is indeed a problem in this scenario. It seems that the first version of the patch is the best and can handle all scenarios. With this patch, the previously merged patches are no longer useful.
I will revert this patch and submit a new fix. Do you have any comments? Revert: https://lore.kernel.org/all/a68c0148e9bf105f9e83ff5e763b8fcb6f7ba9be.1697644299.git....@redhat.com/ New: https://lore.kernel.org/all/20230804052954.2918915-2-fen...@smartx.com/ Thanks, Li > 2024年4月1日 16:43，Yajun Wu <yaj...@nvidia.com> 写道： > > > > On 4/1/2024 4:34 PM, Li Feng wrote: >> >> External email: Use caution opening links or attachments >> >> Hi yajun, >> >> I have submitted a patch to fix this problem a few months ago, but in the >> end this solution was not accepted and other solutions >> were adopted to fix it. >> >> https://lore.kernel.org/all/20230804052954.2918915-2-fen...@smartx.com/ >> > I think this fix is valid. > >> This is the merged fix: >> >> >> https://lore.kernel.org/all/a68c0148e9bf105f9e83ff5e763b8fcb6f7ba9be.1697644299.git....@redhat.com/My >> tests are with this fix, failed in the two scenarios I mentioned. > >> >> Thanks, >> Li >> >>> 2024年4月1日 10:08，Yajun Wu <yaj...@nvidia.com> <mailto:yaj...@nvidia.com> 写道： >>> >>> >>> On 3/27/2024 6:47 PM, Stefano Garzarella wrote: >>>> External email: Use caution opening links or attachments >>>> >>>> >>>> Hi Yajun, >>>> >>>> On Mon, Mar 25, 2024 at 10:54:13AM +0000, Yajun Wu wrote: >>>>> Hi experts, >>>>> >>>>> With latest QEMU (8.2.90), we find two vhost-user-blk backend reconnect >>>>> failure scenarios: >>>> Do you know if has it ever worked and so it's a regression, or have we >>>> always had this problem? >>> >>> I am afraid this commit: "71e076a07d (2022-12-01 02:30:13 -0500) hw/virtio: >>> generalise CHR_EVENT_CLOSED handling" caused both failures. Previous hash >>> is good. >>> >>> I suspect the "if (vhost->vdev)" in vhost_user_async_close_bh is the cause, >>> previous code doesn't have this check? >>> >>>> >>>> Thanks, >>>> Stefano >>>> >>>>> 1. Disconnect vhost-user-blk backend before guest driver probe vblk >>>>> device, then reconnect backend after guest driver probe device. QEMU >>>>> won't send out any vhost messages to restore backend. >>>>> This is because vhost->vdev is NULL before guest driver probe vblk >>>>> device, so vhost_user_blk_disconnect won't be called, s->connected is >>>>> still true. Next vhost_user_blk_connect will simply return without doing >>>>> anything. >>>>> >>>>> 2. modprobe -r virtio-blk inside VM, then disconnect backend, then >>>>> reconnect backend, then modprobe virtio-blk. QEMU won't send messages in >>>>> vhost_dev_init. >>>>> This is because rmmod will let qemu call vhost_user_blk_stop, vhost->vdev >>>>> also become NULL(in vhost_dev_stop), vhost_user_blk_disconnect won't be >>>>> called. Again s->connected is still true, even chr connect is closed. >>>>> >>>>> I think even vhost->vdev is NULL, vhost_user_blk_disconnect should be >>>>> called when chr connect close? >>>>> Hope we can have a fix soon. >>>>> >>>>> >>>>> Thanks, >>>>> Yajun >>>>> >>
