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>
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index d1c0830..79a9f1b 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -21,6 +21,7 @@
int numpages;
pgprot_t mask_set;
pgprot_t mask_clr;
+ int flushtlb;
};
static inline int
@@ -329,11 +330,19 @@
* 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;
}
@@ -438,10 +447,17 @@
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:
*/