Re: [Qemu-devel] [PATCH v4 07/10] s390x/sclp: properly guard pci-specific functions

[Cornelia Huck]

On Tue, 22 Aug 2017 16:27:38 +0200
Halil Pasic <address@hidden> wrote:

> On 08/22/2017 04:06 PM, Cornelia Huck wrote:
> > On Tue, 22 Aug 2017 15:24:34 +0200
> > Cornelia Huck <address@hidden> wrote:
> >   
> >> On Tue, 22 Aug 2017 14:58:37 +0200
> >> Halil Pasic <address@hidden> wrote:
> >>  
> >>> On 08/22/2017 11:39 AM, Cornelia Huck wrote:    
> >>>> On Tue, 22 Aug 2017 11:20:51 +0200
> >>>> Halil Pasic <address@hidden> wrote:  
> >   
> >>>>> Well, the QEMU name of the command is misleading misleading. In the AR
> >>>>> it's called 'Configure I/O Adapter'. The PCI comes into the picture via
> >>>>> byte 8 of the SCCB, the so called adapter type. Valid values for the
> >>>>> adapter type are: 00-01 reserved; 02 PCI function; 03-FF reserved. So
> >>>>> at this point we only have PCI.     
> > 
> > OK, I need one more piece of information. 
> > 
> > We obviously need to check whether the sccb we got is long enough
> > before we try to access the command-specific field. How long is the
> > sccb supposed to be for configure I/O adapter? For pci, 16 bytes; in
> > general, I would guess that it needs to include at least atype and some
> > placeholder for the payload. What does the AR say?
> >  
> 
> The first 2 bytes of the SCCB designate it's length. For this particular
> command it's at least 16 bytes (regardless of pci). The length is
> marked as may be changed by the SCLP.

Thanks for the info, this makes implementing it correctly much easier!

>  
>  
> > Looking at the pci code, I also noted that it cheerfully uses the aid
> > field of the sccb before checking whether it is actually long enough...
> >   
>