Re: [Qemu-devel] [PATCH v1 for-2.12 5/5] s390x/tcg: wire up STORE CHANNEL REPORT WORD

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 4 Dec 2017 18:56:00 +0100
David Hildenbrand <david@redhat.com> wrote:

> On 04.12.2017 18:53, Cornelia Huck wrote:
> > On Mon, 4 Dec 2017 18:34:36 +0100
> > David Hildenbrand <david@redhat.com> wrote:
> >   
> >> On 04.12.2017 18:22, Cornelia Huck wrote:  
> >>> On Mon,  4 Dec 2017 13:55:05 +0100
> >>> David Hildenbrand <david@redhat.com> wrote:
> >>>     
> >>>> We somehow missed that, new kernels require it.    
> >>>
> >>> Why _new_ kernels? I think we have unconditionally issued stcrw since
> >>> back in 2.2?    
> >>
> >> Okay, the problem is then rather related to my setup. No ccw devices ->
> >> no stcrw.
> >>
> >> How could we ever add ccw devices to a TCG guest then?  
> > 
> > Hotplug never worked before your patches. Coldplug does not create
> > machine checks and thus does not trigger the guest to do STCRW. (Only
> > STSCH, in keeping with "all channel I/O acronyms look the same".)
> >   
> 
> But booting Fedora 26/27 without any involved hotplugs (therefore
> machine checks) triggers a STCRW.
> 
> That's how I originally found it. (I started playing with machine checks
> after I had fedora 26/27 running)
> 

Confused. Do you have a backtrace? (Guest/host)