On 06/04/18 15:24, 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 <bsingharora@gmail.com>

Reviewed-by: Rashmica Gupta <redacted>