From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keith Owens Date: Thu, 08 Feb 2007 06:04:30 +0000 Subject: Re: [RFC Patch]Use ar.kr2 for smp_processor_id Message-Id: <6737.1170914670@kao2.melbourne.sgi.com> List-Id: References: <1170905324.3230.7.camel@linux-znh> In-Reply-To: <1170905324.3230.7.camel@linux-znh> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Zou Nan hai (on 08 Feb 2007 11:28:44 +0800) wrote: >Pin ar.kr2 of each CPU, so that smp_processor_id can use it. Historically ar.k2 has been reserved for debugging purposes, for example in ivt.S. Debuggers often need a location that can be used to track progress, it has to be somewhere that does not rely on TLB entries and is guaranteed to appear in MCA/INIT records - ar.k2 is perfect for this. Use Tony's suggestion of testing for a change in ar.k3 (guaranteed to be unique on every cpu) and caching the corresponding cpu number when it changes.