Re: [PATCH 5/5] dax: "Hotplug" persistent memory for use like normal RAM

[Dan Williams]

On Fri, Jan 25, 2019 at 12:20 AM Du, Fan <fan.du@xxxxxxxxx> wrote:
>
> Dan
>
> Thanks for the insights!
>
> Can I say, the UCE is delivered from h/w to OS in a single way in case of machine
> check, only PMEM/DAX stuff filter out UC address and managed in its own way by
> badblocks, if PMEM/DAX doesn't do so, then common RAS workflow will kick in,
> right?

The common RAS workflow always kicks in, it's just the page state
presented by a DAX mapping needs distinct handling. Once it is
hot-plugged it no longer needs to be treated differently than "System
RAM".

> And how about when ARS is involved but no machine check fired for the function
> of this patchset?

The hotplug effectively disconnects this address range from the ARS
results. They will still be reported in the libnvdimm "region" level
badblocks instance, but there's no safe / coordinated way to go clear
those errors without additional kernel enabling. There is no "clear
error" semantic for "System RAM".