On 26.10.23 00:44, 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].
Almost there, I think :)
+static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
+ u64 start, u64 size)
+{
+ unsigned long memblock_size = memory_block_size_bytes();
+ u64 cur_start;
+ int ret;
+
+ 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;
Best to cleanup here instead of handling it in the caller [as noted by
Vishal, we might not be doing that yet]. Using
remove_memory_blocks_and_altmaps() on the fully processed range sounds
reasonable.
maybe something like
ret = arch_add_memory(nid, cur_start, memblock_size, ¶ms);
if (ret) {
kfree(params.altmap);
goto out;
}
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;
}
if (ret && cur_start != start)
remove_memory_blocks_and_altmaps(start, cur_start - start);
return ret;
+
+ /* call arch's memory hotadd */
+ ret = arch_add_memory(nid, cur_start, memblock_size, ¶ms);
+ if (ret < 0) {
+ kfree(params.altmap);
+ return ret;
+ }
+
+ /* 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);
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
[...]
static int check_cpu_on_node(int nid)
{
int cpu;
@@ -2146,11 +2186,69 @@ void try_offline_node(int nid)
}
EXPORT_SYMBOL(try_offline_node);
-static int __ref try_remove_memory(u64 start, u64 size)
+static void __ref remove_memory_blocks_and_altmaps(u64 start, u64 size)
{
- struct memory_block *mem;
- int rc = 0, nid = NUMA_NO_NODE;
+ unsigned long memblock_size = memory_block_size_bytes();
struct vmem_altmap *altmap = NULL;
+ struct memory_block *mem;
+ u64 cur_start;
+ int rc;
+
+ /*
+ * For memmap_on_memory, the altmaps could have been added on
+ * a per-memblock basis. Loop through the entire range if so,
+ * and remove each memblock and its altmap.
+ */
/*
* altmaps where 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) {
+ rc = walk_memory_blocks(cur_start, memblock_size, &mem,
+ test_has_altmap_cb);
+ if (rc) {
+ altmap = mem->altmap;
+ /*
+ * Mark altmap NULL so that we can add a debug
+ * check on memblock free.
+ */
+ mem->altmap = NULL;
+ }
Simpler (especially, we know that there must be an altmap):
mem = find_memory_block(pfn_to_section_nr(cur_start));
altmap = mem->altmap;
mem->altmap = NULL;
I think we might be able to remove test_has_altmap_cb() then.
+
+ remove_memory_block_devices(cur_start, memblock_size);
+
+ arch_remove_memory(cur_start, memblock_size, altmap);
+
+ /* Verify that all vmemmap pages have actually been freed. */
+ if (altmap) {
There must be an altmap, so this can be done unconditionally.
+ WARN(altmap->alloc, "Altmap not fully unmapped");
+ kfree(altmap);
+ }
+ }
+}
--
Cheers,
David / dhildenb
