linux-kernel - [PATCH] xen: don't bother trying to set cr4

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Date:	Wed, 12 Sep 2007 16:44:42 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>
Subject: [PATCH] xen: don't bother trying to set cr4

Xen ignores all updates to cr4, and some versions will kill the domain
if you try to change its value.  Just ignore all changes.

Signed-off-by: Jeremy Fitzhardinge <jeremy@...source.com>
Cc: Andi Kleen <ak@...e.de>

---
 arch/i386/xen/enlighten.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

===================================================================
--- a/arch/i386/xen/enlighten.c
+++ b/arch/i386/xen/enlighten.c
@@ -625,8 +625,8 @@ static unsigned long xen_read_cr2_direct
 
 static void xen_write_cr4(unsigned long cr4)
 {
-	/* never allow TSC to be disabled */
-	native_write_cr4(cr4 & ~X86_CR4_TSD);
+	/* Just ignore cr4 changes; Xen doesn't allow us to do
+	   anything anyway. */
 }
 
 static unsigned long xen_read_cr3(void)


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