On Tue, Mar 27, 2018 at 09:56:47AM +0200, Arnd Bergmann wrote:

On Tue, Mar 27, 2018 at 12:27 AM, Jason Gunthorpe [off-list ref] wrote:

quoted

On Tue, Mar 27, 2018 at 09:01:57AM +1100, Benjamin Herrenschmidt wrote:

quoted

On Mon, 2018-03-26 at 17:46 -0400, Sinan Kaya wrote:

I even see patches adding wmb() based on actual observed memory
corruption during testing on Intel:

https://patchwork.kernel.org/patch/10177207/

So you think all of this is unnecessary and writel is totally strongly
ordered, even on multi-socket Intel?

This example adds a wmb() between two writes to a coherent DMA
area, it is definitely required there.

Ah! So it is, too many things called 'db' in that driver.. One of the
'db' is also WC BAR memory..

Jason