Re: [GIT PULL] device-dax for 5.1: PMEM as RAM

[Linus Torvalds <torvalds@linux-foundation.org>]

On Mon, Mar 11, 2019 at 8:37 AM Dan Williams <dan.j.williams@intel.com> wrote:
>
> Another feature the userspace tooling can support for the PMEM as RAM
> case is the ability to complete an Address Range Scrub of the range
> before it is added to the core-mm. I.e at least ensure that previously
> encountered poison is eliminated.

Ok, so this at least makes sense as an argument to me.

In the "PMEM as filesystem" part, the errors have long-term history,
while in "PMEM as RAM" the memory may be physically the same thing,
but it doesn't have the history and as such may not be prone to
long-term errors the same way.

So that validly argues that yes, when used as RAM, the likelihood for
errors is much lower because they don't accumulate the same way.

> The driver can also publish an
> attribute to indicate when rep; mov is recoverable, and gate the
> hotplug policy on the result. In my opinion a positive indicator of
> the cpu's ability to recover rep; mov exceptions is a gap that needs
> addressing.

Is there some way to say "don't raise MC for this region"? Or at least
limit it to a nonfatal one?

                 Linus