Subject: Re: [1/2] powerpc/mm: Flush cache on memory hot(un)plug

From: Michael Ellerman <[email-masked]>
Date: Tue, 24 Apr 2018 13:48:25 +1000 (AEST)

On Fri, 2018-04-06 at 05:24:23 UTC, Balbir Singh wrote:
> This patch adds support for flushing potentially dirty
> cache lines when memory is hot-plugged/hot-un-plugged.
> The support is currently limited to 64 bit systems.
> 
> The bug was exposed when mappings for a device were
> actually hot-unplugged and plugged in back later.
> A similar issue was observed during the development
> of memtrace, but memtrace does it's own flushing of
> region via a custom routine.
> 
> These patches do a flush both on hotplug/unplug to
> clear any stale data in the cache w.r.t mappings,
> there is a small race window where a clean cache
> line may be created again just prior to tearing
> down the mapping.
> 
> The patches were tested by disabling the flush
> routines in memtrace and doing I/O on the trace
> file. The system immediately checkstops (quite
> reliablly if prior to the hot-unplug of the memtrace
> region, we memset the regions we are about to
> hot unplug). After these patches no custom flushing
> is needed in the memtrace code.
> 
> Signed-off-by: Balbir Singh <[email-masked]>
> Acked-by: Reza Arbab <[email-masked]>
> Reviewed-by: Rashmica Gupta <[email-masked]>

Series applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/fb5924fddf9ee31db04da7ad4e8c34

cheers