linux-kernel - [PATCH 22/25 -v2] turn priviled operation into a macro

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Date:	Fri, 10 Aug 2007 16:12:34 -0300
From:	Glauber de Oliveira Costa <gcosta@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, rusty@...tcorp.com.au, ak@...e.de,
	mingo@...e.hu, chrisw@...s-sol.org, jeremy@...p.org,
	avi@...ranet.com, anthony@...emonkey.ws,
	virtualization@...ts.linux-foundation.org, lguest@...abs.org,
	glommer@...il.com, Glauber de Oliveira Costa <gcosta@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 22/25 -v2] turn priviled operation into a macro

under paravirt, read cr2 cannot be issued directly anymore.
So wrap it in a macro, defined to the operation itself in case
paravirt is off, but to something else if we have paravirt
in the game

Signed-off-by: Glauber de Oliveira Costa <gcosta@...hat.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 arch/x86_64/kernel/head.S |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index e89abcd..1bb6c55 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -18,6 +18,12 @@
 #include <asm/page.h>
 #include <asm/msr.h>
 #include <asm/cache.h>
+#ifdef CONFIG_PARAVIRT
+#include <asm/asm-offsets.h>
+#include <asm/paravirt.h>
+#else
+#define GET_CR2_INTO_RCX mov %cr2, %rcx
+#endif
 
 /* we are not able to switch in one step to the final KERNEL ADRESS SPACE
  * because we need identity-mapped pages.
@@ -267,7 +273,9 @@ ENTRY(early_idt_handler)
 	xorl %eax,%eax
 	movq 8(%rsp),%rsi	# get rip
 	movq (%rsp),%rdx
-	movq %cr2,%rcx
+	/* When PARAVIRT is on, this operation may clobber rax. It is
+	  something safe to do, because we've just zeroed rax. */
+	GET_CR2_INTO_RCX
 	leaq early_idt_msg(%rip),%rdi
 	call early_printk
 	cmpl $2,early_recursion_flag(%rip)
-- 
1.4.4.2

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