Re: How can one find the current processor's id?

From: Eric Hamilton (eric.nospam.hamilton_at_hp.com)
Date: 01/31/05 

Date: Mon, 31 Jan 2005 22:51:56 GMT

Dan Koren <dankoren@yahoo.com> wrote:
> Now however, the kernel must be keeping the id
> of the current processor in a register for its
> own needs, right? Where might that be? ;-)

Disclaimer: The following is release specific implementation details. It
has changed in the past and likely will change in the future.

HP-UX has a concept of a "Per Processor Data Pointer". It is what it
sounds like: a pointer to a per-processor kernel-internal data structure
that is not made available for drivers, trap handlers, applications, etc.
etc.

On PA-RISC, the ppdp is kept in CR_24 (not readable from user space).
On IPF, we currently use ar.k4 (readable from user space).

Neither of those register assignments is architected for compatability or
documented for user use. The information is provided solely for educational
purposes. If you or anyone else needs an extension to the driver
writer's guide to provide an interface to access some sort of processor
identifier, or have another need for a supportable extension to HP-UX,
please work with the DSPP team or file an enhancement request with
the HP support team.

Eric

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