4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Balbir Singh bsingharora@gmail.com
commit fb5924fddf9ee31db04da7ad4e8c3434a387101b upstream.
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.
Fixes: 9d5171a8f248 ("powerpc/powernv: Enable removal of memory for in memory tracing") Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: Balbir Singh bsingharora@gmail.com Acked-by: Reza Arbab arbab@linux.ibm.com Reviewed-by: Rashmica Gupta rashmica.g@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/mm/mem.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -143,6 +143,7 @@ int arch_add_memory(int nid, u64 start, start, start + size, rc); return -EFAULT; } + flush_inval_dcache_range(start, start + size);
return __add_pages(nid, start_pfn, nr_pages, want_memblock); } @@ -171,6 +172,7 @@ int arch_remove_memory(u64 start, u64 si
/* Remove htab bolted mappings for this section of memory */ start = (unsigned long)__va(start); + flush_inval_dcache_range(start, start + size); ret = remove_section_mapping(start, start + size);
/* Ensure all vmalloc mappings are flushed in case they also