MSIX failure

John Baldwin jhb at
Sat Sep 11 11:55:48 UTC 2010

perryh at wrote:
> John Baldwin <jhb at> wrote:
>> On Friday, September 10, 2010 2:55:15 am perryh at wrote:
>>> ...
>>> It is arguably a bug to open O_RDWR when only examining things.
>> You have to have RDWR permission to issue the ioctl to read config
>> registers which pciconf does when examining capabilities.
> So much for avoiding a reboot for <bsd at> (or whatever the
> correct address is -- that one bounced), but now it is beginning to
> look as if there may be a POLA violation at a lower level.  Unless
> there are devices out there whose state can be changed by merely
> _reading_ (not writing) their configuration registers, I would not
> expect to need RDWR permission just to read them.

Umm, not all config registers are standardized and devices are free to 
define device-specific registers with device-specific behavior (many 
do).  Given that, it is quite possible for a device to implement a 
register that takes action when read (e.g. resets to 0 or clears status 
bits, etc.).

pciconf -l itself does not require RDWR permissions, only -c which does 
a good bit more work.

John Baldwin

More information about the freebsd-stable mailing list