From: Andy Lutomirski <luto@kernel.org>
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 <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/69c7d711f240cfec23e6024e940d31af2990db36.1641659630.git.luto@kernel.org
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/mmu_context.h | 2 +-
2 files changed, 2 insertions(+), 1 deletion(-)
Index: linux-2.6/arch/x86/Kconfig
===================================================================
--- linux-2.6.orig/arch/x86/Kconfig
+++ linux-2.6/arch/x86/Kconfig
@@ -133,6 +133,7 @@ config X86
select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if X86_64
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
Index: linux-2.6/arch/x86/include/asm/mmu_context.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/mmu_context.h
+++ linux-2.6/arch/x86/include/asm/mmu_context.h
@@ -175,7 +175,7 @@ extern void switch_mm_irqs_off(struct mm
#define activate_mm(prev, next) \
do { \
paravirt_enter_mmap(next); \
- switch_mm((prev), (next), NULL); \
+ switch_mm_irqs_off((prev), (next), NULL); \
} while (0);
#ifdef CONFIG_X86_32