popf is a horribly expensive instruction, while sti is an optimised fastpath. Switching popf for a conditional branch and sti caused an 8% perf improvement in various linux measurements.
Signed-off-by: Andrew Cooper <[email protected]> --- CC: Jan Beulich <[email protected]> CC: Roger Pau Monné <[email protected]> CC: Wei Liu <[email protected]> --- xen/include/asm-x86/system.h | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/xen/include/asm-x86/system.h b/xen/include/asm-x86/system.h index 65e63de69a67..4be235472ecd 100644 --- a/xen/include/asm-x86/system.h +++ b/xen/include/asm-x86/system.h @@ -267,13 +267,8 @@ static inline unsigned long array_index_mask_nospec(unsigned long index, }) #define local_irq_restore(x) \ ({ \ - BUILD_BUG_ON(sizeof(x) != sizeof(long)); \ - asm volatile ( "pushfq\n\t" \ - "andq %0, (%%rsp)\n\t" \ - "orq %1, (%%rsp)\n\t" \ - "popfq" \ - : : "i?r" ( ~X86_EFLAGS_IF ), \ - "ri" ( (x) & X86_EFLAGS_IF ) ); \ + if ( (x) & X86_EFLAGS_IF ) \ + local_irq_enable(); \ }) static inline int local_irq_is_enabled(void) -- 2.11.0
