Re: [win-pv-devel] XENIFACE not attaching to XENBUS

[RafaÅ WojdyÅa <omeg@xxxxxxxxxxxxxxxxxxxxxx>]

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On 2015-05-20 21:22, RafaÅ WojdyÅa wrote:
> On 2015-05-20 20:53, RafaÅ WojdyÅa wrote:
>> On 2015-05-20 16:15, Paul Durrant wrote:
>>>> -----Original Message----- From: 
>>>> win-pv-devel-bounces@xxxxxxxxxxxxxxxxxxxx
>>>> [mailto:win-pv-devel- bounces@xxxxxxxxxxxxxxxxxxxx] On Behalf
>>>> Of Rafal Wojdyla Sent: 20 May 2015 11:05 To:
>>>> win-pv-devel@xxxxxxxxxxxxxxxxxxxx Subject: [win-pv-devel]
>>>> XENIFACE not attaching to XENBUS
>>>> 
>>> Hello,
>>> 
>>> I've noticed something strange when I was experimenting with 
>>> adding new APIs to Xenbus. I added a Store API to set key 
>>> permissions and incremented the store interface version as
>>> usual (to 2 from 1).
> 
> [...snip...]
> 
>>>> However, since you did not modify the inf, xeniface should 
>>>> still be binding to revision 1 of the PDO and your log shows
>>>>  that is still being created. The doc at 
>>>> https://msdn.microsoft.com/en-us/library/windows/hardware/ff539950%
28v=vs.85%29.aspx
>>>>
>>>> 
says that the maximum number is 64 and there are only 0x28 (40) in
>>>> the list so the old compatible ID should still be there. You
>>>>  should be able to check via device manager to make sure 
>>>> though.
> 
> I think I've got it. We're hitting the other limit mentioned in
> that MSDN page: "The maximum number of characters in a compatible
> ID list, including a NULL terminator after each compatible ID and a
> final NULL terminator, is REGSTR_VAL_MAX_HCID_LEN." This is 1024.
> 1024/40 is 25, but our IDs are longer than that. I guess I'll
> remove the oldest interface versions during testing until some
> better solution is found. : )
> 
I did some more tests and I'm still confused. With the same setup as
above I added the latest PDO revision to XENIFACE's INF file:
XENBUS\VEN_XS0001&DEV_IFACE&REV_00000028
...but it still didn't load. What's weird, registry and the device
manager showed that this ID was indeed registered. It's probably
related to the character limit I mentioned above because when I removed
v1 and v2 interface versions from evtchn, it just started working again.

- -- 
RafaÅ WojdyÅa
Qubes Tools for Windows developer
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