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x86, mtrr: Constify struct mtrr_ops

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This is part of the ops structure constification
effort started by Arjan van de Ven et al.

Benefits of this constification:

 * prevents modification of data that is shared
   (referenced) by many other structure instances
   at runtime

 * detects/prevents accidental (but not intentional)
   modification attempts on archs that enforce
   read-only kernel data at runtime

 * potentially better optimized code as the compiler
   can assume that the const data cannot be changed

 * the compiler/linker move const data into .rodata
   and therefore exclude them from false sharing

Signed-off-by: Emese Revfy <re.emese@gmail.com>
LKML-Reference: <4B65D712.3080804@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
Emese Revfy
2010-01-31 20:16:34 +01:00
committed by H. Peter Anvin
parent ab658321f3
commit 3b9cfc0a99
6 changed files with 10 additions and 10 deletions
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6
arch/x86/kernel/cpu/mtrr/mtrr.h
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@@ -32,7 +32,7 @@ extern int generic_get_free_region(unsigned long base, unsigned long size,
extern int generic_validate_add_page(unsigned long base, unsigned long size,
unsigned int type);
extern struct mtrr_ops generic_mtrr_ops;
extern const struct mtrr_ops generic_mtrr_ops;
extern int positive_have_wrcomb(void);
@@ -53,10 +53,10 @@ void fill_mtrr_var_range(unsigned int index,
u32 base_lo, u32 base_hi, u32 mask_lo, u32 mask_hi);
void get_mtrr_state(void);
extern void set_mtrr_ops(struct mtrr_ops *ops);
extern void set_mtrr_ops(const struct mtrr_ops *ops);
extern u64 size_or_mask, size_and_mask;
extern struct mtrr_ops *mtrr_if;
extern const struct mtrr_ops *mtrr_if;
#define is_cpu(vnd) (mtrr_if && mtrr_if->vendor == X86_VENDOR_##vnd)
#define use_intel() (mtrr_if && mtrr_if->use_intel_if == 1)