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Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()
- From: Andi Kleen <ak at suse dot de>
- To: Brent Casavant <bcasavan at sgi dot com>
- Cc: Chase Venters <chase dot venters at clientec dot com>, Zoltan Menyhart <Zoltan dot Menyhart at bull dot net>, Jes Sorensen <jes at sgi dot com>, Tony Luck <tony dot luck at intel dot com>, discuss at x86-64 dot org, linux-kernel at vger dot kernel dot org, libc-alpha at sourceware dot org, vojtech at suse dot cz, linux-ia64 at vger dot kernel dot org
- Date: Sat, 17 Jun 2006 08:58:39 +0200
- Subject: Re: FOR REVIEW: New x86-64 vsyscall vgetcpu()
- References: <200606140942.31150.ak@suse.de> <Pine.LNX.4.64.0606161615450.23743@turbotaz.ourhouse> <20060616181940.S91827@pkunk.americas.sgi.com>
> That work could form the basis for a low-impact method of exporting
> the current CPU to user space via a read-only mapped page. I'll admit
> to having zero knowledge of whether this would be workable on anything
> other than ia64.
On x86 per CPU mappings are not really feasible. That is because
the CPU uses the Linux page tables directly and to change them
per CPU you would need to fork them per CPU. That would add so much
complications that I don't even want to think them all through ...
-andi