From fb5924fddf9ee31db04da7ad4e8c3434a387101b Mon Sep 17 00:00:00 2001 From: Balbir Singh Date: Fri, 6 Apr 2018 15:24:23 +1000 Subject: [PATCH] powerpc/mm: Flush cache on memory hot(un)plug 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 Acked-by: Reza Arbab Reviewed-by: Rashmica Gupta Signed-off-by: Michael Ellerman --- arch/powerpc/mm/mem.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 737f8a4632cc..c3c39b02b2ba 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -133,6 +133,7 @@ int __meminit arch_add_memory(int nid, u64 start, u64 size, struct vmem_altmap * start, start + size, rc); return -EFAULT; } + flush_inval_dcache_range(start, start + size); return __add_pages(nid, start_pfn, nr_pages, altmap, want_memblock); } @@ -159,6 +160,7 @@ int __meminit arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap /* 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 -- 2.45.2