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powerpc/mm: Add Strong Access Ordering support 

Allow an application to enable Strong Access Ordering on specific pages of
memory on Power 7 hardware. Currently, power has a weaker memory model than
x86. Implementing a stronger memory model allows an emulator to more
efficiently translate x86 code into power code, resulting in faster code
execution.

On Power 7 hardware, storing 0b1110 in the WIMG bits of the hpte enables
strong access ordering mode for the memory page.  This patchset allows a
user to specify which pages are thus enabled by passing a new protection
bit through mmap() and mprotect().  I have defined PROT_SAO to be 0x10.

Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Dave Kleikamp 2008-07-08 00:28:54 +10:00 committed by Benjamin Herrenschmidt
parent 379070491e
commit ef3d3246a0
2 changed files with 33 additions and 0 deletions
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3
arch/powerpc/kernel/syscalls.c
View File

@ -143,6 +143,9 @@ static inline unsigned long do_mmap2(unsigned long addr, size_t len,
struct file * file = NULL;
unsigned long ret = -EINVAL;
if (!arch_validate_prot(prot))
goto out;
if (shift) {
if (off & ((1 << shift) - 1))
goto out;

30
include/asm-powerpc/mman.h
View File

@ -1,7 +1,9 @@
#ifndef _ASM_POWERPC_MMAN_H
#define _ASM_POWERPC_MMAN_H
#include <asm/cputable.h>
#include <asm-generic/mman.h>
#include <linux/mm.h>
/*
* This program is free software; you can redistribute it and/or
@ -26,4 +28,32 @@
#define MAP_POPULATE 0x8000 /* populate (prefault) pagetables */
#define MAP_NONBLOCK 0x10000 /* do not block on IO */
#ifdef CONFIG_PPC64
/*
* This file is included by linux/mman.h, so we can't use cacl_vm_prot_bits()
* here. How important is the optimization?
*/
static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot)
{
return (prot & PROT_SAO) ? VM_SAO : 0;
}
#define arch_calc_vm_prot_bits(prot) arch_calc_vm_prot_bits(prot)
static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
{
return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : 0;
}
#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags)
static inline int arch_validate_prot(unsigned long prot)
{
if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
return 0;
if ((prot & PROT_SAO) && !cpu_has_feature(CPU_FTR_SAO))
return 0;
return 1;
}
#define arch_validate_prot(prot) arch_validate_prot(prot)
#endif /* CONFIG_PPC64 */
#endif /* _ASM_POWERPC_MMAN_H */