[Xen-devel] [PATCH 06/16] xen: disable PAT

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Ian Campbell <ian.campbell@xxxxxxxxxx>

Xen imposes a particular PAT layout on all paravirtual guests which
does not match the layout Linux would like to use.

Force PAT to be disabled until this is resolved.

[ Impact: disable PAT under Xen, due to incompatible configurations ]

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/include/asm/pat.h |    5 +++++
 arch/x86/mm/pat.c          |    7 +------
 arch/x86/xen/enlighten.c   |    3 +++
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 7af14e5..fe7be93 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -6,8 +6,13 @@
 
 #ifdef CONFIG_X86_PAT
 extern int pat_enabled;
+extern void pat_disable(const char *reason);
 #else
 static const int pat_enabled;
+static inline void pat_disable(const char *reason)
+{
+       (void)reason;
+}
 #endif
 
 extern void pat_init(void);
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index e6718bb..5ba8d88 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -31,7 +31,7 @@
 #ifdef CONFIG_X86_PAT
 int __read_mostly pat_enabled = 1;
 
-static inline void pat_disable(const char *reason)
+void pat_disable(const char *reason)
 {
        pat_enabled = 0;
        printk(KERN_INFO "%s\n", reason);
@@ -43,11 +43,6 @@ static int __init nopat(char *str)
        return 0;
 }
 early_param("nopat", nopat);
-#else
-static inline void pat_disable(const char *reason)
-{
-       (void)reason;
-}
 #endif
 
 
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 50580fc..89f47da 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -51,6 +51,7 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/reboot.h>
+#include <asm/pat.h>
 
 #include "xen-ops.h"
 #include "mmu.h"
@@ -1085,6 +1086,8 @@ asmlinkage void __init xen_start_kernel(void)
                add_preferred_console("hvc", 0, NULL);
        }
 
+       pat_disable("PAT disabled on Xen");
+
        xen_raw_console_write("about to get started...\n");
 
        /* Start the world */
-- 
1.6.0.6


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