Re: [PATCH] x86: Add an explicit barrier() to clflushopt()

On Mon, Oct 19, 2015 at 12:05:29PM +0100, Chris Wilson wrote:

In order to add the clobbers, I had to adjust the macro slightly:

+#define alternative_output(oldinstr, newinstr, feature, output) \

•   asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
  

•           : output : "i" (0) : "memory")
  
  

and that also works. The concern I have here is that the asm does use "+m" as its output already, and the clflush() asm doesn't require the manual clobber.

Yeah, you could make the above

#define alternative_output(oldinstr, newinstr, feature, output, clobber...)

and use it to define clflushopt(). hpa might have a better idea, though...