How to use bts recording?

[Metzger, Markus T]

Hello Simon,

>> Are you maybe using virtualization?
>
>Rechecked with the server team: yes, the old RHEL kernel runs on Redhat
>Virtualization Manager; the newer one on VMware vSphere.

Here's the problem.  AFAIK neither BTS nor PT are virtualized.  This is simply
missing enabling in hypervisors.  They do properly indicate this by omitting
the respective cpuid enumeration.  This results in an EOPNOTSUPP when
GDB tries to enable it, which is printed by GDB.

From that perspective, the error message was all correct.  What's missing is
why it is not supported.  All that GDB knows is that the OS told it that this is
not supported.

I'm afraid that's a fairly common problem, these days, but I don't see how
GDB could check that it is running in a guest OS and that the hypervisor did
not virtualize PT or BTS.

GDB could grep for the respective flags in /proc/cpuinfo but it would really
only confirm what the OS already told it: it is not supported.

Regards,
Markus.

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