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

[Halil Pasic]

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.
 
 
> 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...
>