[23/23] x86/mm: Opt in to IRQs-off activate_mm()

Commit Message

Andy Lutomirski Jan. 8, 2022, 4:44 p.m. UTC

We gain nothing by having the core code enable IRQs right before calling
activate_mm() only for us to turn them right back off again in switch_mm().

This will save a few cycles, so execve() should be blazingly fast with this
patch applied!

Signed-off-by: Andy Lutomirski <[e-mail]>
---
 arch/x86/Kconfig                   | 1 +
 arch/x86/include/asm/mmu_context.h | 8 ++++----
 2 files changed, 5 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5060c38bf560..908a596619f2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -119,6 +119,7 @@  config X86
 	select ARCH_WANT_LD_ORPHAN_WARN
 	select ARCH_WANTS_THP_SWAP		if X86_64
 	select ARCH_HAS_PARANOID_L1D_FLUSH
+	select ARCH_WANT_IRQS_OFF_ACTIVATE_MM
 	select BUILDTIME_TABLE_SORT
 	select CLKEVT_I8253
 	select CLOCKSOURCE_VALIDATE_LAST_CYCLE
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 2ca4fc4a8a0a..f028f1b68bc0 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -132,10 +132,10 @@  extern void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
 			       struct task_struct *tsk);
 #define switch_mm_irqs_off switch_mm_irqs_off
 
-#define activate_mm(prev, next)			\
-do {						\
-	paravirt_activate_mm((prev), (next));	\
-	switch_mm((prev), (next), NULL);	\
+#define activate_mm(prev, next)				\
+do {							\
+	paravirt_activate_mm((prev), (next));		\
+	switch_mm_irqs_off((prev), (next), NULL);	\
 } while (0);
 
 #ifdef CONFIG_X86_32