[PATCH v2 1/3] powerpc/booke64: add sync after writing PTE

[Scott Wood]

On Mon, 2013-09-16 at 07:38 +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2013-09-13 at 22:50 -0500, Scott Wood wrote:
> > The ISA says that a sync is needed to order a PTE write with a
> > subsequent hardware tablewalk lookup.  On e6500, without this sync
> > we've been observed to die with a DSI due to a PTE write not being seen
> > by a subsequent access, even when everything happens on the same
> > CPU.
> 
> This is gross, I didn't realize we had that bogosity in the
> architecture...
> 
> Did you measure the performance impact ?

I didn't see a noticeable impact on the tests I ran, but those were
aimed at measuring TLB miss overhead.  I'll need to try it with a
benchmark that's more oriented around lots of page table updates.

-Scott