x86: add noclflush option

To disable CLFLUSH usage, especially in change_page_attr().

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index b8fadf5f75a3..040e30a33b7c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1191,6 +1191,8 @@ and is between 256 and 4096 characters. It is defined in the file
                         register save and restore. The kernel will only save
                         legacy floating-point registers on task switch.
 
+        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
+
         nohlt           [BUGS=ARM]
 
         no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index dfc9563fc4f0..56b7ea8e6c79 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -542,6 +542,13 @@ void __cpuinit detect_ht(struct cpuinfo_x86 *c)
 }
 #endif
 
+static __init int setup_noclflush(char *arg)
+{
+        setup_clear_cpu_cap(X86_FEATURE_CLFLSH);
+        return 1;
+}
+__setup("noclflush", setup_noclflush);
+
 void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
 {
         char *vendor = NULL;
diff --git a/arch/x86/kernel/setup_64.c b/arch/x86/kernel/setup_64.c
index df159520bbd2..cb9b8a90c094 100644
--- a/arch/x86/kernel/setup_64.c
+++ b/arch/x86/kernel/setup_64.c
@@ -1032,6 +1032,13 @@ void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
 
 }
 
+static __init int setup_noclflush(char *arg)
+{
+        setup_clear_cpu_cap(X86_FEATURE_CLFLSH);
+        return 1;
+}
+__setup("noclflush", setup_noclflush);
+
 void __cpuinit print_cpu_info(struct cpuinfo_x86 *c)
 {
         if (c->x86_model_id[0])