linux-kernel - [patch]pageattr: cache flush before tlb flush

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Date:	Mon, 18 Aug 2008 10:27:31 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
Subject: [patch]pageattr: cache flush before tlb flush

clflush uses a virtual address but cache line is physical indexed in
x86. In my understanding, clflush will do some pagetable walk, so doing
cache flush first should reduce some pagetable walk.

Signed-off-by: Shaohua Li <shaohua.li@...el.com>

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index f5f5154..d8b24df 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -168,10 +168,8 @@ static void cpa_flush_range(unsigned long start, int numpages, int cache)
 	BUG_ON(irqs_disabled());
 	WARN_ON(PAGE_ALIGN(start) != start);
 
-	on_each_cpu(__cpa_flush_range, NULL, 1);
-
 	if (!cache)
-		return;
+		goto tlb_flush;
 
 	/*
 	 * We only need to flush on one CPU,
@@ -188,6 +186,9 @@ static void cpa_flush_range(unsigned long start, int numpages, int cache)
 		if (pte && (pte_val(*pte) & _PAGE_PRESENT))
 			clflush_cache_range((void *) addr, PAGE_SIZE);
 	}
+
+tlb_flush:
+	on_each_cpu(__cpa_flush_range, NULL, 1);
 }
 
 /*


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