Commit-ID: 478dc89cf316697e8029411a64ea2b30c528434d Gitweb: http://git.kernel.org/tip/478dc89cf316697e8029411a64ea2b30c528434d Author: Andy Lutomirski <luto@xxxxxxxxxx> AuthorDate: Thu, 12 Nov 2015 12:59:04 -0800 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Tue, 24 Nov 2015 09:56:44 +0100 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@xxxxxxxxxx> Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: Brian Gerst <brgerst@xxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: H. Peter Anvin <hpa@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/73ee804fff48cd8c66b65b724f9f728a11a8c686.1447361906.git.luto@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- arch/x86/entry/calling.h | 15 +++++++++++++++ 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 3c71dd9..e32206e 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 a55697d..9d34d3c 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: -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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