RE: [PATCH v10 08/10] btrace, linux: Enable ptwrite packets.

["Metzger, Markus T" <markus.t.metzger@intel.com>]

Hello Felix,

>> >+#if (LIBIPT_VERSION >= 0x200)
>> >+  record_btrace_conf.pt.ptwrite = true;
>> >+#else
>> >+  record_btrace_conf.pt.ptwrite = false;
>> >+#endif
>>
>> Is there a way to get an error when attempting to install a custom
>> ptwrite filter when either GDB (via libipt) or the kernel does not
>> support PTWRITE?
>
>Good point. Unfortunately I don't see one with the current design.
>Currently we just cache the filter functions in python when one is
>registered. The configuration isn't exposed to the python layer in
>any way.
>
>I am not sure how we could do this. Exposing "maint btrace info"
>and parsing that would be one way, not sure if we want to go down
>that path.

We could warn at decode-time when applying the ptwrite filter.
We should have different warning texts for GDB (via libipt) not
supporting ptwrite and the system (kernel or h/w) not supporting it.

Not as good as an error when installing the ptwrite filter but better
than wondering why it isn't working as expected.

Regards,
Markus.
Intel Deutschland GmbH
Registered Address: Am Campeon 10, 85579 Neubiberg, Germany
Tel: +49 89 99 8853-0, www.intel.de <http://www.intel.de>
Managing Directors: Christin Eisenschmid, Sharon Heck, Tiffany Doon Silva  
Chairperson of the Supervisory Board: Nicole Lau
Registered Office: Munich
Commercial Register: Amtsgericht Muenchen HRB 186928