[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/3] x86/irq: local_irq_restore() should not blindly popf
On 21/10/13 14:41, Andrew Cooper wrote: > local_irq_restore() should only be concerned with possibly changing the > interrupt flag. A blind popf could corrupt other system flags. > > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> > CC: Keir Fraser <keir@xxxxxxx> > CC: Jan Beulich <JBeulich@xxxxxxxx> > --- > xen/include/asm-x86/system.h | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/xen/include/asm-x86/system.h b/xen/include/asm-x86/system.h > index 6ab7d56..cbf0f6a 100644 > --- a/xen/include/asm-x86/system.h > +++ b/xen/include/asm-x86/system.h > @@ -159,8 +159,10 @@ static always_inline unsigned long __cmpxchg( > #define local_irq_restore(x) \ > ({ \ > BUILD_BUG_ON(sizeof(x) != sizeof(long)); \ > - asm volatile ( "push" __OS " %0 ; popf" __OS \ > - : : "g" (x) : "memory", "cc" ); \ > + if ( x & X86_EFLAGS_IF ) \ > + local_irq_enable(); \ > + else \ > + local_irq_disable(); \ > }) This adds a branch in a potentially hot path. Is the local_irq_disable() needed? Interrupts should already be disabled on entry. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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