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x86: cpa, check if we changed anything and tlb flushing is necessary 

Flush tlbs only when there was a real change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Thomas Gleixner 2008-02-04 16:48:07 +01:00 committed by Ingo Molnar
parent 72e458dfa6
commit f4ae5da0e8
1 changed files with 17 additions and 1 deletions
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18
arch/x86/mm/pageattr.c
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@ -21,6 +21,7 @@ struct cpa_data {
int numpages;
pgprot_t mask_set;
pgprot_t mask_clr;
int flushtlb;
};
static inline int
@ -329,11 +330,19 @@ static int __change_page_attr(unsigned long address, struct cpa_data *cpa)
* not the memory it points to
*/
new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
set_pte_atomic(kpte, new_pte);
/*
* Do we really change anything ?
*/
if (pte_val(old_pte) != pte_val(new_pte)) {
set_pte_atomic(kpte, new_pte);
cpa->flushtlb = 1;
}
} else {
err = split_large_page(kpte, address);
if (!err)
goto repeat;
cpa->flushtlb = 1;
}
return err;
}
@ -438,9 +447,16 @@ static int change_page_attr_set_clr(unsigned long addr, int numpages,
cpa.numpages = numpages;
cpa.mask_set = mask_set;
cpa.mask_clr = mask_clr;
cpa.flushtlb = 0;
ret = __change_page_attr_set_clr(&cpa);
/*
* Check whether we really changed something:
*/
if (!cpa.flushtlb)
return ret;
/*
* No need to flush, when we did not set any of the caching
* attributes: