diff options
| author | Andy Lutomirski <luto@kernel.org> | 2015-11-12 12:59:04 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-11-24 09:56:44 +0100 |
| commit | 478dc89cf316697e8029411a64ea2b30c528434d (patch) | |
| tree | f2d9b65ba366429ab2f8932e01d05a96d4efe492 /arch/x86 | |
| parent | 2671c3e4fe2a34bd9bf2eecdf5d1149d4b55dbdf (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.h | 15 | ||||
| -rw-r--r-- | arch/x86/entry/entry_64.S | 8 |
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: |