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Commit ef3d3246 authored by Dave Kleikamp's avatar Dave Kleikamp Committed by Benjamin Herrenschmidt
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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: default avatarDave Kleikamp <shaggy@linux.vnet.ibm.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 37907049

arch/powerpc/kernel/syscalls.c

+3 −0
Original line number Diff line number Diff line
@@ -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;

include/asm-powerpc/mman.h

+30 −0
Original line number Diff line number Diff line 
#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 */