Volatile in Wintun

[Jason A. Donenfeld]

Hi Lev,

I spent a while squinting at assembly diffs and reviewing how the
linux kernel does things. Voila:
https://git.zx2c4.com/wintun/commit/?id=c072f4f3c4b540c7cfebec563b0fb5d7ba932b6f

> Does it mean that hardware reordering

I'm mostly concerned here with the compiler reordering accesses,
actually. With regards to hardware memory barriers, I haven't seen
places yet where we'd need an explicit smp_mb() or similar that's not
already provided by the various locks. But let me know if your
analysis concludes differently.

Jason