RE: [PATCH] vhost-user-scsi: implement handle_output

[Liu, Changpeng]

There is some logic in vhost_user_blk_handle_output() for now, it's not empty 
as vhost-user-scsi.
There should be other issue if it can't start from SeaBIOS.

> -----Original Message-----
> From: Felipe Franciosi [mailto:address@hidden]
> Sent: Monday, October 21, 2019 4:00 PM
> To: Yongji Xie <address@hidden>; Liu, Changpeng
> <address@hidden>
> Cc: Stefan Hajnoczi <address@hidden>; Alex Williamson
> <address@hidden>; Dr . David Alan Gilbert <address@hidden>;
> address@hidden
> Subject: Re: [PATCH] vhost-user-scsi: implement handle_output
> 
> 
> 
> > On Oct 21, 2019, at 5:01 AM, Yongji Xie <address@hidden> wrote:
> >
> > On Fri, 18 Oct 2019 at 19:14, Felipe Franciosi <address@hidden> wrote:
> >>
> >>
> >>
> >>> On Oct 18, 2019, at 3:59 AM, Yongji Xie <address@hidden> wrote:
> >>>
> >>> On Fri, 18 Oct 2019 at 01:17, Felipe Franciosi <address@hidden> wrote:
> >>>>
> >>>> Originally, vhost-user-scsi did not implement a handle_output callback
> >>>> as that didn't seem necessary. Turns out it is.
> >>>>
> >>>> Depending on which other devices are presented to a VM, SeaBIOS may
> >>>> decide to map vhost-user-scsi devices on the 64-bit range of the address
> >>>> space. As a result, SeaBIOS will kick VQs via the config space. Those
> >>>> land on Qemu (not the vhost backend) and are missed, causing the VM not
> >>>> to boot. This fixes the issue by getting Qemu to post the notification.
> >>>>
> >>> Should we fix this in vhost-user-blk too?
> >>
> >> I'm not sure vhost-user-blk suffers from the same problem. Certainly
> >
> > Actually I found vhost-user-blk has the same problem in a mutilple
> > GPUs passthough environment.
> 
> Let's Cc Changpeng for comments. I'm not familiar with that code.
> 
> In any case, I still think we should merge this and fix other
> implementations separately. That allows us to revert patches
> individually if anything else breaks.
> 
> F.
> 
> >
> > Thanks,
> > Yongji