From: Rashmica Gupta rashmica.g@gmail.com
[ Upstream commit 3f7daf3d7582dc6628ac40a9045dd1bbd80c5f35 ]
When hot-removing memory release_mem_region_adjustable() splits iomem resources if they are not the exact size of the memory being hot-deleted. Adding this memory back to the kernel adds a new resource.
Eg a node has memory 0x0 - 0xfffffffff. Hot-removing 1GB from 0xf40000000 results in the single resource 0x0-0xfffffffff being split into two resources: 0x0-0xf3fffffff and 0xf80000000-0xfffffffff.
When we hot-add the memory back we now have three resources: 0x0-0xf3fffffff, 0xf40000000-0xf7fffffff, and 0xf80000000-0xfffffffff.
This is an issue if we try to remove some memory that overlaps resources. Eg when trying to remove 2GB at address 0xf40000000, release_mem_region_adjustable() fails as it expects the chunk of memory to be within the boundaries of a single resource. We then get the warning: "Unable to release resource" and attempting to use memtrace again gives us this error: "bash: echo: write error: Resource temporarily unavailable"
This patch makes memtrace remove memory in chunks that are always the same size from an address that is always equal to end_of_memory - n*size, for some n. So hotremoving and hotadding memory of different sizes will now not attempt to remove memory that spans multiple resources.
Signed-off-by: Rashmica Gupta rashmica.g@gmail.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/platforms/powernv/memtrace.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c index fc222a0c2ac4..c9a6d4f3403c 100644 --- a/arch/powerpc/platforms/powernv/memtrace.c +++ b/arch/powerpc/platforms/powernv/memtrace.c @@ -119,17 +119,15 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE, change_memblock_state);
- lock_device_hotplug(); - remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT); - unlock_device_hotplug();
return true; }
static u64 memtrace_alloc_node(u32 nid, u64 size) { - u64 start_pfn, end_pfn, nr_pages; + u64 start_pfn, end_pfn, nr_pages, pfn; u64 base_pfn; + u64 bytes = memory_block_size_bytes();
if (!NODE_DATA(nid) || !node_spanned_pages(nid)) return 0; @@ -142,8 +140,21 @@ static u64 memtrace_alloc_node(u32 nid, u64 size) end_pfn = round_down(end_pfn - nr_pages, nr_pages);
for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { - if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) + if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) { + /* + * Remove memory in memory block size chunks so that + * iomem resources are always split to the same size and + * we never try to remove memory that spans two iomem + * resources. + */ + lock_device_hotplug(); + end_pfn = base_pfn + nr_pages; + for (pfn = base_pfn; pfn < end_pfn; pfn += bytes>> PAGE_SHIFT) { + remove_memory(nid, pfn << PAGE_SHIFT, bytes); + } + unlock_device_hotplug(); return base_pfn << PAGE_SHIFT; + } }
return 0;