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x86: fold pda into percpu area on SMP

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[ Based on original patch from Christoph Lameter and Mike Travis. ]

Currently pdas and percpu areas are allocated separately.  %gs points
to local pda and percpu area can be reached using pda->data_offset.
This patch folds pda into percpu area.

Due to strange gcc requirement, pda needs to be at the beginning of
the percpu area so that pda->stack_canary is at %gs:40.  To achieve
this, a new percpu output section macro - PERCPU_VADDR_PREALLOC() - is
added and used to reserve pda sized chunk at the start of the percpu
area.

After this change, for boot cpu, %gs first points to pda in the
data.init area and later during setup_per_cpu_areas() gets updated to
point to the actual pda.  This means that setup_per_cpu_areas() need
to reload %gs for CPU0 while clearing pda area for other cpus as cpu0
already has modified it when control reaches setup_per_cpu_areas().

This patch also removes now unnecessary get_local_pda() and its call
sites.

A lot of this patch is taken from Mike Travis' "x86_64: Fold pda into
per cpu area" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo
2009-01-13 20:41:35 +09:00
committed by Ingo Molnar
parent c8f3329a0d
commit 1a51e3a0ae
11 changed files with 104 additions and 144 deletions
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25
include/asm-generic/vmlinux.lds.h
View File

@@ -441,9 +441,10 @@
. = __per_cpu_load + SIZEOF(.data.percpu);
/**
* PERCPU_VADDR - define output section for percpu area
* PERCPU_VADDR_PREALLOC - define output section for percpu area with prealloc
* @vaddr: explicit base address (optional)
* @phdr: destination PHDR (optional)
* @prealloc: the size of prealloc area
*
* Macro which expands to output section for percpu area. If @vaddr
* is not blank, it specifies explicit base address and all percpu
@@ -455,11 +456,33 @@
* section in the linker script will go there too. @phdr should have
* a leading colon.
*
* If @prealloc is non-zero, the specified number of bytes will be
* reserved at the start of percpu area. As the prealloc area is
* likely to break alignment, this macro puts areas in increasing
* alignment order.
*
* This macro defines three symbols, __per_cpu_load, __per_cpu_start
* and __per_cpu_end. The first one is the vaddr of loaded percpu
* init data. __per_cpu_start equals @vaddr and __per_cpu_end is the
* end offset.
*/
#define PERCPU_VADDR_PREALLOC(vaddr, segment, prealloc) \
PERCPU_PROLOG(vaddr) \
. += prealloc; \
*(.data.percpu) \
*(.data.percpu.shared_aligned) \
*(.data.percpu.page_aligned) \
PERCPU_EPILOG(segment)
/**
* PERCPU_VADDR - define output section for percpu area
* @vaddr: explicit base address (optional)
* @phdr: destination PHDR (optional)
*
* Macro which expands to output section for percpu area. Mostly
* identical to PERCPU_VADDR_PREALLOC(@vaddr, @phdr, 0) other than
* using slighly different layout.
*/
#define PERCPU_VADDR(vaddr, phdr) \
PERCPU_PROLOG(vaddr) \
*(.data.percpu.page_aligned) \