From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keith Owens <kaos@sgi.com>
Date: Sat, 04 Feb 2006 00:16:09 +0000
Subject: Re: ia64 printk_clock()
Message-Id: <15306.1139012169@ocs3>
List-Id: <linux-ia64.vger.kernel.org>
References: <20060202204422.GA27082@sgi.com>
In-Reply-To: <20060202204422.GA27082@sgi.com>
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To: linux-ia64@vger.kernel.org

"Luck, Tony" (on Fri, 3 Feb 2006 10:43:08 -0800) wrote:
>> Now that I read the whole thread, how about remove pining DTR 
>> requirement for per-cpu data?  In alt_dtlb_miss, we can just
>> detect whether ifa is per_cpu address and read ar.k3 to get the
>> physical address, then insert a TC.  That will free up a tlb
>> entry for application to use.
>
>What will you do when someone accesses per-cpu area before ar.k3
>has been initialized (the bug that we are trying to fix here)?
>
>This would add some extra code to the Alt-DTLB handler.  Could
>you hide all/most of the extra latency?
>
>Are there any correctness issues?  Any place where we access a
>per-cpu variable where we absolutely cannot take an Alt-DTLB fault?

mca_asm.S, GET_IA64_MCA_DATA().  ia64_mca_data is per cpu and is
accessed right from the start of the MCA/INIT handlers, with psr.i,
psr.ic both 0.