Re: [kvm-unit-tests v2 4/8] x86: eventinj: make test work with -O0

[Paolo Bonzini <pbonzini@redhat.com>]

On 03/03/2016 02:09, Peter Feiner wrote:
> With optimizations disabled, the compiler generated a call for
> irq_enable() -- rather than just inlining an sti instruction as
> expected. Thus the irq_enable ret would run in the sti shadow and the
> vectors would fire in the wrong order.
> 
> Signed-off-by: Peter Feiner <pfeiner@google.com>
> ---
>  x86/eventinj.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/x86/eventinj.c b/x86/eventinj.c
> index bddedce..202ac19 100644
> --- a/x86/eventinj.c
> +++ b/x86/eventinj.c
> @@ -296,8 +296,7 @@ int main()
>  	apic_self_ipi(32);
>  	flush_stack();
>  	io_delay();
> -	irq_enable();
> -	asm volatile ("int $33");
> +	asm volatile ("sti; int $33");
>  	irq_disable();
>  	printf("After vec 32 and int $33\n");
>  	report("vec 32/int $33", test_count == 2);
> 

I've added a comment to irq_enable too:

/* Note that irq_enable() does not ensure an interrupt shadow due
 * to the vagaries of compiler optimizations.  If you need the
 * shadow, use a single asm with "sti" and the instruction after it.
 */


Paolo