linux-kernel - [patch] paravirt: VDSO page is essential

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Message-ID: <20070305120631.GA14105@elte.hu>
Date:	Mon, 5 Mar 2007 13:06:31 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Roland McGrath <roland@...hat.com>,
	Andi Kleen <ak@...e.de>, Rusty Russell <rusty@...tcorp.com.au>
Subject: [patch] paravirt: VDSO page is essential

Subject: [patch] paravirt: VDSO page is essential
From: Ingo Molnar <mingo@...e.hu>

commit 3bbf54725467d604698721384d858b5983b87e8f disables the VDSO for 
CONFIG_PARAVIRT kernels. This #ifdeffery was a bad change: the VDSO is 
an essential component of Linux, and this change forces all of them to 
use int $0x80 - including sane ones like KVM. (If a hypervisor does not 
handle the VDSO properly then it can work things around via the vdso=0 
boot option. Or CONFIG_PARAVIRT should not have been merged. But in any 
case, it is a basic taste issue: we DO NOT #ifdef around core features 
like this!)

Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/i386/kernel/sysenter.c |    4 ----
 1 file changed, 4 deletions(-)

Index: linux/arch/i386/kernel/sysenter.c
===================================================================
--- linux.orig/arch/i386/kernel/sysenter.c
+++ linux/arch/i386/kernel/sysenter.c
@@ -27,11 +27,7 @@
  * Should the kernel map a VDSO page into processes and pass its
  * address down to glibc upon exec()?
  */
-#ifdef CONFIG_PARAVIRT
-unsigned int __read_mostly vdso_enabled = 0;
-#else
 unsigned int __read_mostly vdso_enabled = 1;
-#endif
 
 EXPORT_SYMBOL_GPL(vdso_enabled);
 
-
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