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authorAndy Lutomirski <luto@kernel.org>2015-11-12 12:59:04 -0800
committerIngo Molnar <mingo@kernel.org>2015-11-24 09:56:44 +0100
commit478dc89cf316697e8029411a64ea2b30c528434d (patch)
treef2d9b65ba366429ab2f8932e01d05a96d4efe492 /arch/x86
parent2671c3e4fe2a34bd9bf2eecdf5d1149d4b55dbdf (diff)
x86/entry/64: Bypass enter_from_user_mode on non-context-tracking boots
On CONFIG_CONTEXT_TRACKING kernels that have context tracking disabled at runtime (which includes most distro kernels), we still have the overhead of a call to enter_from_user_mode in interrupt and exception entries. If jump labels are available, this uses the jump label infrastructure to skip the call. Signed-off-by: Andy Lutomirski <luto@kernel.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/73ee804fff48cd8c66b65b724f9f728a11a8c686.1447361906.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/entry/calling.h15
-rw-r--r--arch/x86/entry/entry_64.S8
2 files changed, 17 insertions, 6 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 3c71dd947c7b..e32206e09868 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -1,3 +1,5 @@
+#include <linux/jump_label.h>
+
/*
x86 function call convention, 64-bit:
@@ -232,3 +234,16 @@ For 32-bit we have the following conventions - kernel is built with
#endif /* CONFIG_X86_64 */
+/*
+ * This does 'call enter_from_user_mode' unless we can avoid it based on
+ * kernel config or using the static jump infrastructure.
+ */
+.macro CALL_enter_from_user_mode
+#ifdef CONFIG_CONTEXT_TRACKING
+#ifdef HAVE_JUMP_LABEL
+ STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
+#endif
+ call enter_from_user_mode
+.Lafter_call_\@:
+#endif
+.endm
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index a55697d19824..9d34d3cfceb6 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -520,9 +520,7 @@ END(irq_entries_start)
*/
TRACE_IRQS_OFF
-#ifdef CONFIG_CONTEXT_TRACKING
- call enter_from_user_mode
-#endif
+ CALL_enter_from_user_mode
1:
/*
@@ -1066,9 +1064,7 @@ ENTRY(error_entry)
* (which can take locks).
*/
TRACE_IRQS_OFF
-#ifdef CONFIG_CONTEXT_TRACKING
- call enter_from_user_mode
-#endif
+ CALL_enter_from_user_mode
ret
.Lerror_entry_done: