Re: [RFC 2/2] Add SN2 Special Memory driver.

[Christoph Hellwig <hch@infradead.org>]

> Index: linux-2.6/arch/ia64/sn/kernel/mspec.c
> =================================> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6/arch/ia64/sn/kernel/mspec.c	2004-09-09 10:53:55.000000000 -0500
> @@ -0,0 +1,658 @@
> +/*
> + * SN Platform Special Memory (mspec) Support
> + *
> + * This driver exports the SN special memory (mspec) facility to user processes.
> + * There are three types of memory made available thru this driver:
> + * fetchops, uncached and cached.
> + *
> + * Fetchops are atomic memory operations that are implemented in the
> + * memory controller on SGI SN hardware.
> + *
> + * Uncached are used for memory write combining feature of the ia64
> + * cpu.
> + *
> + * Cached are used for areas of memory that are used as cached addresses
> + * on our partition and used as uncached addresses from other partitions.
> + * Due to a design constraint of the SN2 Shub, you can not have processors
> + * on the same FSB perform both a cached and uncached reference to the
> + * same cache line.  These special memory cached regions prevent the
> + * kernel from ever dropping in a TLB entry and therefore prevent the
> + * processor from ever speculating a cache line from this page.
> + */
> +
> +/*
> + * Copyright (C) 2001-2004 Silicon Graphics, Inc.  All rights
> + * reserved.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of version 2 of the GNU General Public License
> + * as published by the Free Software Foundation.
> + */

Usually the copyright headerz is before the description.

Index: linux-2.6/mm/page_alloc.c
> =================================> --- linux-2.6.orig/mm/page_alloc.c	2004-09-09 09:22:31.000000000 -0500
> +++ linux-2.6/mm/page_alloc.c	2004-09-09 10:53:55.000000000 -0500
> @@ -42,6 +42,7 @@
>  int numnodes = 1;
>  int sysctl_lower_zone_protection = 0;
>  
> +EXPORT_SYMBOL(numnodes);

Umm, we had that as part of the xp module already and don't want this one
as a public API.

>  
>  /*
> + * Walks the EFI memory map and calls 'callback' once for each EFI memory
> + * descriptor that has memory marked as only EFI_MEMORY_UC.
> + */
> +void
> +efi_memmap_walk_uc (efi_freemem_callback_t callback, void *arg)

See the thread starting in
http://www.gelato.unsw.edu.au/linux-ia64/0307/6218.html how to do this
properly.