On 06/12/2021 13:38, Andrew Cooper wrote: > 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(); \ > })
Bah. There's still the one total abuse of local_irq_restore() to disable interrupts. I'll do a pre-requisite patch. ~Andrew
