linux-kernel - Re: [patches] [PATCH] [4/12] x86_64: Disable CLFLUSH support again

Open Source and information security mailing list archives

Date:	Thu, 09 Aug 2007 13:54:27 +0100
From:	"Jan Beulich" <jbeulich@...ell.com>
To:	"Andi Kleen" <ak@...e.de>
Cc:	<linux-kernel@...r.kernel.org>, <patches@...-64.org>
Subject: Re: [patches] [PATCH] [4/12] x86_64: Disable CLFLUSH support
	again

The 64-bit conditional seems wrong to me, I'd assume you mean

	if (1 || !cpu_has_clflush)

Jan

>>> Andi Kleen <ak@...e.de> 09.08.07 14:41 >>>

It turns out CLFLUSH support is still not complete; we
flush the wrong pages.  Again disable it for the release.
Noticed by Jan Beulich.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/i386/mm/pageattr.c   |    2 +-
 arch/x86_64/mm/pageattr.c |    3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

Index: linux/arch/i386/mm/pageattr.c
===================================================================

--- linux.orig/arch/i386/mm/pageattr.c
+++ linux/arch/i386/mm/pageattr.c
@@ -82,7 +82,7 @@ static void flush_kernel_map(void *arg)
 	struct page *p;
 
 	/* High level code is not ready for clflush yet */
-	if (cpu_has_clflush) {
+	if (0 && cpu_has_clflush) {
 		list_for_each_entry (p, lh, lru)
 			cache_flush_page(p);
 	} else if (boot_cpu_data.x86_model >= 4)
Index: linux/arch/x86_64/mm/pageattr.c
===================================================================
--- linux.orig/arch/x86_64/mm/pageattr.c
+++ linux/arch/x86_64/mm/pageattr.c
@@ -75,7 +75,8 @@ static void flush_kernel_map(void *arg)
 
 	/* When clflush is available always use it because it is
 	   much cheaper than WBINVD. */
-	if (!cpu_has_clflush)
+	/* clflush is still broken. Disable for now. */
+	if (0 && !cpu_has_clflush)
 		asm volatile("wbinvd" ::: "memory");
 	else list_for_each_entry(pg, l, lru) {
 		void *adr = page_address(pg);
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