On Wed, Nov 01, 2023 at 04:51:52PM -0600, 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; > + > + altmap = mem->altmap; > + mem->altmap = NULL; > + > + remove_memory_block_devices(cur_start, memblock_size); Is cur_start always aligned to memory_block_size_bytes? If not, the above function will return directly, is that a issue? Fan > + > + arch_remove_memory(cur_start, memblock_size, altmap); > + > + /* Verify that all vmemmap pages have actually been freed. */ > + WARN(altmap->alloc, "Altmap not fully unmapped"); > + kfree(altmap); > + } > +} > + > +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; > + > + /* 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)) > + remove_memory_blocks_and_altmaps(start, cur_start - start); > + return ret; > +} > + > /* > * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > * and online/offline operations (triggered e.g. by sysfs). > @@ -1390,10 +1468,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > { > struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > enum memblock_flags memblock_flags = MEMBLOCK_NONE; > - struct vmem_altmap mhp_altmap = { > - .base_pfn = PHYS_PFN(res->start), > - .end_pfn = PHYS_PFN(res->end), > - }; > struct memory_group *group = NULL; > u64 start, size; > bool new_node = false; > @@ -1436,28 +1510,22 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > /* > * Self hosted memmap array > */ > - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { > - if (mhp_supports_memmap_on_memory(size)) { > - mhp_altmap.free = memory_block_memmap_on_memory_pages(); > - params.altmap = kmemdup(&mhp_altmap, > - sizeof(struct vmem_altmap), > - GFP_KERNEL); > - if (!params.altmap) > - goto error; > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && > + mhp_supports_memmap_on_memory(memory_block_size_bytes())) { > + ret = create_altmaps_and_memory_blocks(nid, group, start, size); > + if (ret) > + goto error; > + } else { > + ret = arch_add_memory(nid, start, size, ¶ms); > + if (ret < 0) > + goto error; > + > + /* create memory block devices after memory was added */ > + ret = create_memory_block_devices(start, size, NULL, group); > + if (ret) { > + arch_remove_memory(start, size, NULL); > + goto error; > } > - /* fallback to not using altmap */ > - } > - > - /* call arch's memory hotadd */ > - ret = arch_add_memory(nid, start, size, ¶ms); > - if (ret < 0) > - goto error_free; > - > - /* create memory block devices after memory was added */ > - ret = create_memory_block_devices(start, size, params.altmap, group); > - if (ret) { > - arch_remove_memory(start, size, NULL); > - goto error_free; > } > > if (new_node) { > @@ -1494,8 +1562,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > walk_memory_blocks(start, size, NULL, online_memory_block); > > return ret; > -error_free: > - kfree(params.altmap); > error: > if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) > memblock_remove(start, size); > @@ -2062,17 +2128,13 @@ static int check_memblock_offlined_cb(struct memory_block *mem, void *arg) > return 0; > } > > -static int test_has_altmap_cb(struct memory_block *mem, void *arg) > +static int count_memory_range_altmaps_cb(struct memory_block *mem, void *arg) > { > - struct memory_block **mem_ptr = (struct memory_block **)arg; > - /* > - * return the memblock if we have altmap > - * and break callback. > - */ > - if (mem->altmap) { > - *mem_ptr = mem; > - return 1; > - } > + u64 *num_altmaps = (u64 *)arg; > + > + if (mem->altmap) > + *num_altmaps += 1; > + > return 0; > } > > @@ -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"); > + return -EINVAL; > + } > + > + return 1; > +} > + > static int __ref try_remove_memory(u64 start, u64 size) > { > - struct memory_block *mem; > - int rc = 0, nid = NUMA_NO_NODE; > - struct vmem_altmap *altmap = NULL; > + int rc, nid = NUMA_NO_NODE; > > BUG_ON(check_hotplug_memory_range(start, size)); > > @@ -2167,45 +2249,25 @@ static int __ref try_remove_memory(u64 start, u64 size) > if (rc) > return rc; > > - /* > - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in > - * the same granularity it was added - a single memory block. > - */ > - if (mhp_memmap_on_memory()) { > - rc = walk_memory_blocks(start, size, &mem, test_has_altmap_cb); > - if (rc) { > - if (size != memory_block_size_bytes()) { > - pr_warn("Refuse to remove %#llx - %#llx," > - "wrong granularity\n", > - start, start + size); > - return -EINVAL; > - } > - altmap = mem->altmap; > - /* > - * Mark altmap NULL so that we can add a debug > - * check on memblock free. > - */ > - mem->altmap = NULL; > - } > - } > - > /* 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; > + } else if (rc == 0) { > + /* > + * Memory block device removal under the device_hotplug_lock is > + * a barrier against racing online attempts. > + * No altmaps present, do the removal directly > + */ > + remove_memory_block_devices(start, size); > + arch_remove_memory(start, size, NULL); > + } else { > + /* all memblocks in the range have altmaps */ > + remove_memory_blocks_and_altmaps(start, size); > } > > if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) { > @@ -2218,8 +2280,9 @@ static int __ref try_remove_memory(u64 start, u64 size) > if (nid != NUMA_NO_NODE) > try_offline_node(nid); > > +err: > mem_hotplug_done(); > - return 0; > + return (rc < 0 ? rc : 0); > } > > /** > > -- > 2.41.0 >
