On 2020-02-27 10:43 a.m., Jason Gunthorpe wrote: > Hm, AFAIK WC memory is not compatible with the spinlocks/mutexs/etc in > Linux, so while it is true the memory has no side effects, there would > be surprising concurrency risks if anything in the kernel tried to > write to it. > > Not compatible means the locks don't contain stores to WC memory the > way you would expect. AFAIK on many CPUs extra barriers are required > to keep WC stores ordered, the same way ARM already has extra barriers > to keep UC stores ordered with locking.. > > The spinlocks are defined to contain UC stores though. > > If there is no actual need today for WC I would suggest using UC as > the default. Ok, that sounds sensible. I'll do that in the next revision. Thanks, Logan
