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[PATCH] i386: Convert PDA into the percpu section

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Currently x86 (similar to x84-64) has a special per-cpu structure
called "i386_pda" which can be easily and efficiently referenced via
the %fs register.  An ELF section is more flexible than a structure,
allowing any piece of code to use this area.  Indeed, such a section
already exists: the per-cpu area.

So this patch:
(1) Removes the PDA and uses per-cpu variables for each current member.
(2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU.
(3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which
    can be used to calculate addresses for this CPU's variables.
(4) Simplifies startup, because %fs doesn't need to be loaded with a
    special segment at early boot; it can be deferred until the first
    percpu area is allocated (or never for UP).

The result is less code and one less x86-specific concept.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
This commit is contained in:
Jeremy Fitzhardinge 2007-05-02 19:27:16 +02:00 • committed by Andi Kleen
commit 7c3576d261
17 changed files with 177 additions and 195 deletions
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6
include/asm-i386/segment.h
View file

@ -39,7 +39,7 @@
* 25 - APM BIOS support
*
* 26 - ESPFIX small SS
* 27 - PDA [ per-cpu private data area ]
* 27 - per-cpu [ offset to per-cpu data area ]
* 28 - unused
* 29 - unused
* 30 - unused
@ -74,8 +74,8 @@
#define GDT_ENTRY_ESPFIX_SS (GDT_ENTRY_KERNEL_BASE + 14)
#define __ESPFIX_SS (GDT_ENTRY_ESPFIX_SS * 8)
#define GDT_ENTRY_PDA (GDT_ENTRY_KERNEL_BASE + 15)
#define __KERNEL_PDA (GDT_ENTRY_PDA * 8)
#define GDT_ENTRY_PERCPU (GDT_ENTRY_KERNEL_BASE + 15)
#define __KERNEL_PERCPU (GDT_ENTRY_PERCPU * 8)
#define GDT_ENTRY_DOUBLEFAULT_TSS 31