On 01.11.23 23:51, Vishal Verma wrote:
The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to
'memblock_size' chunks of memory being added. Adding a larger span of
memory precludes memmap_on_memory semantics.
For users of hotplug such as kmem, large amounts of memory might get
added from the CXL subsystem. In some cases, this amount may exceed the
available 'main memory' to store the memmap for the memory being added.
In this case, it is useful to have a way to place the memmap on the
memory being added, even if it means splitting the addition into
memblock-sized chunks.
Change add_memory_resource() to loop over memblock-sized chunks of
memory if caller requested memmap_on_memory, and if other conditions for
it are met. Teach try_remove_memory() to also expect that a memory
range being removed might have been split up into memblock sized chunks,
and to loop through those as needed.
This does preclude being able to use PUD mappings in the direct map; a
proposal to how this could be optimized in the future is laid out
here[1].
[1]: https://lore.kernel.org/linux-mm/b6753402-2de9-25b2-36e9-eacd49752b19@xxxxxxxxxx/
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
---
mm/memory_hotplug.c | 213 ++++++++++++++++++++++++++++++++++------------------
1 file changed, 138 insertions(+), 75 deletions(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 6be7de9efa55..d242e49d7f7b 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1380,6 +1380,84 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
return arch_supports_memmap_on_memory(vmemmap_size);
}
+static void __ref remove_memory_blocks_and_altmaps(u64 start, u64 size)
+{
+ unsigned long memblock_size = memory_block_size_bytes();
+ u64 cur_start;
+
+ /*
+ * For memmap_on_memory, the altmaps were added on a per-memblock
+ * basis; we have to process each individual memory block.
+ */
+ for (cur_start = start; cur_start < start + size;
+ cur_start += memblock_size) {
+ struct vmem_altmap *altmap = NULL;
+ struct memory_block *mem;
+
+ mem = find_memory_block(pfn_to_section_nr(PFN_DOWN(cur_start)));
+ WARN_ON_ONCE(!mem);
+ if (!mem)
+ continue;
Nit:
if (WARN_ON_ONCE(!mem))
continue;
+ for (cur_start = start; cur_start < start + size;
+ cur_start += memblock_size) {
+ struct mhp_params params = { .pgprot =
+ pgprot_mhp(PAGE_KERNEL) };
+ struct vmem_altmap mhp_altmap = {
+ .base_pfn = PHYS_PFN(cur_start),
+ .end_pfn = PHYS_PFN(cur_start + memblock_size - 1),
+ };
+
+ mhp_altmap.free = memory_block_memmap_on_memory_pages();
+ params.altmap = kmemdup(&mhp_altmap, sizeof(struct vmem_altmap),
+ GFP_KERNEL);
+ if (!params.altmap)
+ return -ENOMEM;
As already spotted, we have to cleanup.
+
+ /* call arch's memory hotadd */
+ ret = arch_add_memory(nid, cur_start, memblock_size, ¶ms);
+ if (ret < 0) {
+ kfree(params.altmap);
+ goto out;
+ }
+
+ /* create memory block devices after memory was added */
+ ret = create_memory_block_devices(cur_start, memblock_size,
+ params.altmap, group);
+ if (ret) {
+ arch_remove_memory(cur_start, memblock_size, NULL);
+ kfree(params.altmap);
+ goto out;
+ }
+ }
+
+ return 0;
+out:
+ if (ret && (cur_start != start))
Nit: I think you can drop the inner parentheses.
@@ -2146,11 +2208,31 @@ void try_offline_node(int nid)
}
EXPORT_SYMBOL(try_offline_node);
+static int memory_blocks_have_altmaps(u64 start, u64 size)
+{
+ u64 num_memblocks = size / memory_block_size_bytes();
+ u64 num_altmaps = 0;
+
+ if (!mhp_memmap_on_memory())
+ return 0;
+
+ walk_memory_blocks(start, size, &num_altmaps,
+ count_memory_range_altmaps_cb);
+
+ if (num_altmaps == 0)
+ return 0;
+
+ if (num_memblocks != num_altmaps) {
+ WARN_ONCE(1, "Not all memblocks in range have altmaps");
Nit:
if (WARN_ON_ONCE(num_memblocks != num_altmaps))
return -EINVAL;
Should be sufficient.
[...]
/* remove memmap entry */
firmware_map_remove(start, start + size, "System RAM");
- /*
- * Memory block device removal under the device_hotplug_lock is
- * a barrier against racing online attempts.
- */
- remove_memory_block_devices(start, size);
-
mem_hotplug_begin();
- arch_remove_memory(start, size, altmap);
-
- /* Verify that all vmemmap pages have actually been freed. */
- if (altmap) {
- WARN(altmap->alloc, "Altmap not fully unmapped");
- kfree(altmap);
+ rc = memory_blocks_have_altmaps(start, size);
+ if (rc < 0) {
+ goto err;
Nit: Maybe better to just
if (rc < 0) {
mem_hotplug_done();
return rc
} else ...
And avoid the error label below. Makes the code easier to read.
+ } else if (rc == 0) {
Nit: else if (!rc)
With the cleanup fixed,
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
--
Cheers,
David / dhildenb
